zig fmt

51 files changed, 191 insertions, 204 deletions

diff --git a/lib/std/c.zig b/lib/std/c.zig
index 9f1114b9c1..0f166b7e59 100644
--- a/lib/std/c.zig
+++ b/lib/std/c.zig
@@ -217,7 +217,7 @@ pub extern "c" fn utimes(path: [*:0]const u8, times: *[2]timeval) c_int;
 pub extern "c" fn utimensat(dirfd: fd_t, pathname: [*:0]const u8, times: *[2]timespec, flags: u32) c_int;
 pub extern "c" fn futimens(fd: fd_t, times: *const [2]timespec) c_int;
 
-pub extern "c" fn pthread_create(noalias newthread: *pthread_t, noalias attr: ?*const pthread_attr_t, start_routine: extern fn (?*c_void) ?*c_void, noalias arg: ?*c_void) c_int;
+pub extern "c" fn pthread_create(noalias newthread: *pthread_t, noalias attr: ?*const pthread_attr_t, start_routine: fn (?*c_void) callconv(.C) ?*c_void, noalias arg: ?*c_void) c_int;
 pub extern "c" fn pthread_attr_init(attr: *pthread_attr_t) c_int;
 pub extern "c" fn pthread_attr_setstack(attr: *pthread_attr_t, stackaddr: *c_void, stacksize: usize) c_int;
 pub extern "c" fn pthread_attr_setguardsize(attr: *pthread_attr_t, guardsize: usize) c_int;
diff --git a/lib/std/c/dragonfly.zig b/lib/std/c/dragonfly.zig
index a271b2e869..0c859018be 100644
--- a/lib/std/c/dragonfly.zig
+++ b/lib/std/c/dragonfly.zig
@@ -9,7 +9,7 @@ pub extern "c" fn getdents(fd: c_int, buf_ptr: [*]u8, nbytes: usize) usize;
 pub extern "c" fn sigaltstack(ss: ?*stack_t, old_ss: ?*stack_t) c_int;
 pub extern "c" fn getrandom(buf_ptr: [*]u8, buf_len: usize, flags: c_uint) isize;
 
-pub const dl_iterate_phdr_callback = extern fn (info: *dl_phdr_info, size: usize, data: ?*c_void) c_int;
+pub const dl_iterate_phdr_callback = fn (info: *dl_phdr_info, size: usize, data: ?*c_void) callconv(.C) c_int;
 pub extern "c" fn dl_iterate_phdr(callback: dl_iterate_phdr_callback, data: ?*c_void) c_int;
 
 pub const pthread_mutex_t = extern struct {
diff --git a/lib/std/c/freebsd.zig b/lib/std/c/freebsd.zig
index 3a0634dbb7..ea52c05f0b 100644
--- a/lib/std/c/freebsd.zig
+++ b/lib/std/c/freebsd.zig
@@ -24,7 +24,7 @@ pub extern "c" fn sendfile(
     flags: u32,
 ) c_int;
 
-pub const dl_iterate_phdr_callback = extern fn (info: *dl_phdr_info, size: usize, data: ?*c_void) c_int;
+pub const dl_iterate_phdr_callback = fn (info: *dl_phdr_info, size: usize, data: ?*c_void) callconv(.C) c_int;
 pub extern "c" fn dl_iterate_phdr(callback: dl_iterate_phdr_callback, data: ?*c_void) c_int;
 
 pub const pthread_mutex_t = extern struct {
diff --git a/lib/std/c/linux.zig b/lib/std/c/linux.zig
index 1da0db57d6..4ceeb5a773 100644
--- a/lib/std/c/linux.zig
+++ b/lib/std/c/linux.zig
@@ -75,7 +75,7 @@ pub extern "c" fn inotify_add_watch(fd: fd_t, pathname: [*]const u8, mask: u32)
 /// See std.elf for constants for this
 pub extern "c" fn getauxval(__type: c_ulong) c_ulong;
 
-pub const dl_iterate_phdr_callback = extern fn (info: *dl_phdr_info, size: usize, data: ?*c_void) c_int;
+pub const dl_iterate_phdr_callback = fn (info: *dl_phdr_info, size: usize, data: ?*c_void) callconv(.C) c_int;
 pub extern "c" fn dl_iterate_phdr(callback: dl_iterate_phdr_callback, data: ?*c_void) c_int;
 
 pub extern "c" fn sigaltstack(ss: ?*stack_t, old_ss: ?*stack_t) c_int;
diff --git a/lib/std/c/netbsd.zig b/lib/std/c/netbsd.zig
index 20960b3f77..31adbb1f59 100644
--- a/lib/std/c/netbsd.zig
+++ b/lib/std/c/netbsd.zig
@@ -6,7 +6,7 @@ usingnamespace std.c;
 extern "c" fn __errno() *c_int;
 pub const _errno = __errno;
 
-pub const dl_iterate_phdr_callback = extern fn (info: *dl_phdr_info, size: usize, data: ?*c_void) c_int;
+pub const dl_iterate_phdr_callback = fn (info: *dl_phdr_info, size: usize, data: ?*c_void) callconv(.C) c_int;
 pub extern "c" fn dl_iterate_phdr(callback: dl_iterate_phdr_callback, data: ?*c_void) c_int;
 
 pub extern "c" fn arc4random_buf(buf: [*]u8, len: usize) void;
diff --git a/lib/std/event/channel.zig b/lib/std/event/channel.zig
index 83c77bcac5..5aef0bb3ba 100644
--- a/lib/std/event/channel.zig
+++ b/lib/std/event/channel.zig
@@ -105,7 +105,7 @@ pub fn Channel(comptime T: type) type {
 
         /// await this function to get an item from the channel. If the buffer is empty, the frame will
         /// complete when the next item is put in the channel.
-        pub async fn get(self: *SelfChannel) T {
+        pub fn get(self: *SelfChannel) callconv(.Async) T {
             // TODO https://github.com/ziglang/zig/issues/2765
             var result: T = undefined;
             var my_tick_node = Loop.NextTickNode.init(@frame());
@@ -305,8 +305,7 @@ test "std.event.Channel wraparound" {
     channel.put(7);
     testing.expectEqual(@as(i32, 7), channel.get());
 }
-
-async fn testChannelGetter(channel: *Channel(i32)) void {
+fn testChannelGetter(channel: *Channel(i32)) callconv(.Async) void {
     const value1 = channel.get();
     testing.expect(value1 == 1234);
 
@@ -321,12 +320,10 @@ async fn testChannelGetter(channel: *Channel(i32)) void {
     testing.expect(value4.? == 4444);
     await last_put;
 }
-
-async fn testChannelPutter(channel: *Channel(i32)) void {
+fn testChannelPutter(channel: *Channel(i32)) callconv(.Async) void {
     channel.put(1234);
     channel.put(4567);
 }
-
-async fn testPut(channel: *Channel(i32), value: i32) void {
+fn testPut(channel: *Channel(i32), value: i32) callconv(.Async) void {
     channel.put(value);
 }
diff --git a/lib/std/event/future.zig b/lib/std/event/future.zig
index 51a63e90ee..5de22c574c 100644
--- a/lib/std/event/future.zig
+++ b/lib/std/event/future.zig
@@ -34,7 +34,7 @@ pub fn Future(comptime T: type) type {
         /// Obtain the value. If it's not available, wait until it becomes
         /// available.
         /// Thread-safe.
-        pub async fn get(self: *Self) *T {
+        pub fn get(self: *Self) callconv(.Async) *T {
             if (@atomicLoad(Available, &self.available, .SeqCst) == .Finished) {
                 return &self.data;
             }
@@ -59,7 +59,7 @@ pub fn Future(comptime T: type) type {
         /// should start working on the data.
         /// It's not required to call start() before resolve() but it can be useful since
         /// this method is thread-safe.
-        pub async fn start(self: *Self) ?*T {
+        pub fn start(self: *Self) callconv(.Async) ?*T {
             const state = @cmpxchgStrong(Available, &self.available, .NotStarted, .Started, .SeqCst, .SeqCst) orelse return null;
             switch (state) {
                 .Started => {
diff --git a/lib/std/event/group.zig b/lib/std/event/group.zig
index 5eebb7ffbc..155a9486b7 100644
--- a/lib/std/event/group.zig
+++ b/lib/std/event/group.zig
@@ -84,7 +84,7 @@ pub fn Group(comptime ReturnType: type) type {
         /// Wait for all the calls and promises of the group to complete.
         /// Thread-safe.
         /// Safe to call any number of times.
-        pub async fn wait(self: *Self) ReturnType {
+        pub fn wait(self: *Self) callconv(.Async) ReturnType {
             const held = self.lock.acquire();
             defer held.release();
 
@@ -127,8 +127,7 @@ test "std.event.Group" {
 
     const handle = async testGroup(std.heap.page_allocator);
 }
-
-async fn testGroup(allocator: *Allocator) void {
+fn testGroup(allocator: *Allocator) callconv(.Async) void {
     var count: usize = 0;
     var group = Group(void).init(allocator);
     var sleep_a_little_frame = async sleepALittle(&count);
@@ -145,20 +144,17 @@ async fn testGroup(allocator: *Allocator) void {
     another.add(&something_that_fails_frame) catch @panic("memory");
     testing.expectError(error.ItBroke, another.wait());
 }
-
-async fn sleepALittle(count: *usize) void {
+fn sleepALittle(count: *usize) callconv(.Async) void {
     std.time.sleep(1 * std.time.millisecond);
     _ = @atomicRmw(usize, count, .Add, 1, .SeqCst);
 }
-
-async fn increaseByTen(count: *usize) void {
+fn increaseByTen(count: *usize) callconv(.Async) void {
     var i: usize = 0;
     while (i < 10) : (i += 1) {
         _ = @atomicRmw(usize, count, .Add, 1, .SeqCst);
     }
 }
-
-async fn doSomethingThatFails() anyerror!void {}
-async fn somethingElse() anyerror!void {
+fn doSomethingThatFails() callconv(.Async) anyerror!void {}
+fn somethingElse() callconv(.Async) anyerror!void {
     return error.ItBroke;
 }
diff --git a/lib/std/event/lock.zig b/lib/std/event/lock.zig
index ff1f738c5e..179b881c9c 100644
--- a/lib/std/event/lock.zig
+++ b/lib/std/event/lock.zig
@@ -89,7 +89,7 @@ pub const Lock = struct {
         while (self.queue.get()) |node| resume node.data;
     }
 
-    pub async fn acquire(self: *Lock) Held {
+    pub fn acquire(self: *Lock) callconv(.Async) Held {
         var my_tick_node = Loop.NextTickNode.init(@frame());
 
         errdefer _ = self.queue.remove(&my_tick_node); // TODO test canceling an acquire
@@ -134,8 +134,7 @@ test "std.event.Lock" {
     const expected_result = [1]i32{3 * @intCast(i32, shared_test_data.len)} ** shared_test_data.len;
     testing.expectEqualSlices(i32, &expected_result, &shared_test_data);
 }
-
-async fn testLock(lock: *Lock) void {
+fn testLock(lock: *Lock) callconv(.Async) void {
     var handle1 = async lockRunner(lock);
     var tick_node1 = Loop.NextTickNode{
         .prev = undefined,
@@ -167,8 +166,7 @@ async fn testLock(lock: *Lock) void {
 
 var shared_test_data = [1]i32{0} ** 10;
 var shared_test_index: usize = 0;
-
-async fn lockRunner(lock: *Lock) void {
+fn lockRunner(lock: *Lock) callconv(.Async) void {
     suspend; // resumed by onNextTick
 
     var i: usize = 0;
diff --git a/lib/std/event/locked.zig b/lib/std/event/locked.zig
index 5e9c0ea10e..e921803447 100644
--- a/lib/std/event/locked.zig
+++ b/lib/std/event/locked.zig
@@ -31,7 +31,7 @@ pub fn Locked(comptime T: type) type {
             self.lock.deinit();
         }
 
-        pub async fn acquire(self: *Self) HeldLock {
+        pub fn acquire(self: *Self) callconv(.Async) HeldLock {
             return HeldLock{
                 // TODO guaranteed allocation elision
                 .held = self.lock.acquire(),
diff --git a/lib/std/event/loop.zig b/lib/std/event/loop.zig
index 15e7a3481c..e55d5116b9 100644
--- a/lib/std/event/loop.zig
+++ b/lib/std/event/loop.zig
@@ -503,7 +503,7 @@ pub const Loop = struct {
         }
     }
 
-    pub async fn bsdWaitKev(self: *Loop, ident: usize, filter: i16, fflags: u32) void {
+    pub fn bsdWaitKev(self: *Loop, ident: usize, filter: i16, fflags: u32) callconv(.Async) void {
         var resume_node = ResumeNode.Basic{
             .base = ResumeNode{
                 .id = ResumeNode.Id.Basic,
diff --git a/lib/std/event/rwlock.zig b/lib/std/event/rwlock.zig
index 425088063f..7a47c27dd8 100644
--- a/lib/std/event/rwlock.zig
+++ b/lib/std/event/rwlock.zig
@@ -97,7 +97,7 @@ pub const RwLock = struct {
         while (self.reader_queue.get()) |node| resume node.data;
     }
 
-    pub async fn acquireRead(self: *RwLock) HeldRead {
+    pub fn acquireRead(self: *RwLock) callconv(.Async) HeldRead {
         _ = @atomicRmw(usize, &self.reader_lock_count, .Add, 1, .SeqCst);
 
         suspend {
@@ -130,7 +130,7 @@ pub const RwLock = struct {
         return HeldRead{ .lock = self };
     }
 
-    pub async fn acquireWrite(self: *RwLock) HeldWrite {
+    pub fn acquireWrite(self: *RwLock) callconv(.Async) HeldWrite {
         suspend {
             var my_tick_node = Loop.NextTickNode{
                 .data = @frame(),
@@ -225,8 +225,7 @@ test "std.event.RwLock" {
     const expected_result = [1]i32{shared_it_count * @intCast(i32, shared_test_data.len)} ** shared_test_data.len;
     testing.expectEqualSlices(i32, expected_result, shared_test_data);
 }
-
-async fn testLock(allocator: *Allocator, lock: *RwLock) void {
+fn testLock(allocator: *Allocator, lock: *RwLock) callconv(.Async) void {
     var read_nodes: [100]Loop.NextTickNode = undefined;
     for (read_nodes) |*read_node| {
         const frame = allocator.create(@Frame(readRunner)) catch @panic("memory");
@@ -259,8 +258,7 @@ const shared_it_count = 10;
 var shared_test_data = [1]i32{0} ** 10;
 var shared_test_index: usize = 0;
 var shared_count: usize = 0;
-
-async fn writeRunner(lock: *RwLock) void {
+fn writeRunner(lock: *RwLock) callconv(.Async) void {
     suspend; // resumed by onNextTick
 
     var i: usize = 0;
@@ -277,8 +275,7 @@ async fn writeRunner(lock: *RwLock) void {
         shared_test_index = 0;
     }
 }
-
-async fn readRunner(lock: *RwLock) void {
+fn readRunner(lock: *RwLock) callconv(.Async) void {
     suspend; // resumed by onNextTick
     std.time.sleep(1);
 
diff --git a/lib/std/event/rwlocked.zig b/lib/std/event/rwlocked.zig
index 3f4c6ddbf8..9a569e8f1f 100644
--- a/lib/std/event/rwlocked.zig
+++ b/lib/std/event/rwlocked.zig
@@ -40,14 +40,14 @@ pub fn RwLocked(comptime T: type) type {
             self.lock.deinit();
         }
 
-        pub async fn acquireRead(self: *Self) HeldReadLock {
+        pub fn acquireRead(self: *Self) callconv(.Async) HeldReadLock {
             return HeldReadLock{
                 .held = self.lock.acquireRead(),
                 .value = &self.locked_data,
             };
         }
 
-        pub async fn acquireWrite(self: *Self) HeldWriteLock {
+        pub fn acquireWrite(self: *Self) callconv(.Async) HeldWriteLock {
             return HeldWriteLock{
                 .held = self.lock.acquireWrite(),
                 .value = &self.locked_data,
diff --git a/lib/std/os/bits/darwin.zig b/lib/std/os/bits/darwin.zig
index d116d6157a..8a596331a6 100644
--- a/lib/std/os/bits/darwin.zig
+++ b/lib/std/os/bits/darwin.zig
@@ -125,7 +125,7 @@ pub const empty_sigset = sigset_t(0);
 
 /// Renamed from `sigaction` to `Sigaction` to avoid conflict with function name.
 pub const Sigaction = extern struct {
-    handler: extern fn (c_int) void,
+    handler: fn (c_int) callconv(.C) void,
     sa_mask: sigset_t,
     sa_flags: c_int,
 };
diff --git a/lib/std/os/bits/dragonfly.zig b/lib/std/os/bits/dragonfly.zig
index 6a6c871fc5..df22678323 100644
--- a/lib/std/os/bits/dragonfly.zig
+++ b/lib/std/os/bits/dragonfly.zig
@@ -458,9 +458,9 @@ pub const S_IFSOCK = 49152;
 pub const S_IFWHT = 57344;
 pub const S_IFMT = 61440;
 
-pub const SIG_ERR = @intToPtr(extern fn (i32) void, maxInt(usize));
-pub const SIG_DFL = @intToPtr(extern fn (i32) void, 0);
-pub const SIG_IGN = @intToPtr(extern fn (i32) void, 1);
+pub const SIG_ERR = @intToPtr(fn (i32) callconv(.C) void, maxInt(usize));
+pub const SIG_DFL = @intToPtr(fn (i32) callconv(.C) void, 0);
+pub const SIG_IGN = @intToPtr(fn (i32) callconv(.C) void, 1);
 pub const BADSIG = SIG_ERR;
 pub const SIG_BLOCK = 1;
 pub const SIG_UNBLOCK = 2;
@@ -519,13 +519,13 @@ pub const sigset_t = extern struct {
 pub const sig_atomic_t = c_int;
 pub const Sigaction = extern struct {
     __sigaction_u: extern union {
-        __sa_handler: ?extern fn (c_int) void,
-        __sa_sigaction: ?extern fn (c_int, [*c]siginfo_t, ?*c_void) void,
+        __sa_handler: ?fn (c_int) callconv(.C) void,
+        __sa_sigaction: ?fn (c_int, [*c]siginfo_t, ?*c_void) callconv(.C) void,
     },
     sa_flags: c_int,
     sa_mask: sigset_t,
 };
-pub const sig_t = [*c]extern fn (c_int) void;
+pub const sig_t = [*c]fn (c_int) callconv(.C) void;
 
 pub const sigvec = extern struct {
     sv_handler: [*c]__sighandler_t,
diff --git a/lib/std/os/bits/freebsd.zig b/lib/std/os/bits/freebsd.zig
index 9999dca62f..eee7504366 100644
--- a/lib/std/os/bits/freebsd.zig
+++ b/lib/std/os/bits/freebsd.zig
@@ -725,16 +725,16 @@ pub const winsize = extern struct {
 
 const NSIG = 32;
 
-pub const SIG_ERR = @intToPtr(extern fn (i32) void, maxInt(usize));
-pub const SIG_DFL = @intToPtr(extern fn (i32) void, 0);
-pub const SIG_IGN = @intToPtr(extern fn (i32) void, 1);
+pub const SIG_ERR = @intToPtr(fn (i32) callconv(.C) void, maxInt(usize));
+pub const SIG_DFL = @intToPtr(fn (i32) callconv(.C) void, 0);
+pub const SIG_IGN = @intToPtr(fn (i32) callconv(.C) void, 1);
 
 /// Renamed from `sigaction` to `Sigaction` to avoid conflict with the syscall.
 pub const Sigaction = extern struct {
     /// signal handler
     __sigaction_u: extern union {
-        __sa_handler: extern fn (i32) void,
-        __sa_sigaction: extern fn (i32, *__siginfo, usize) void,
+        __sa_handler: fn (i32) callconv(.C) void,
+        __sa_sigaction: fn (i32, *__siginfo, usize) callconv(.C) void,
     },
 
     /// see signal options
diff --git a/lib/std/os/bits/linux.zig b/lib/std/os/bits/linux.zig
index 750b487754..438be2299b 100644
--- a/lib/std/os/bits/linux.zig
+++ b/lib/std/os/bits/linux.zig
@@ -813,15 +813,15 @@ pub const app_mask: sigset_t = [2]u32{ 0xfffffffc, 0x7fffffff } ++ [_]u32{0xffff
 pub const k_sigaction = if (is_mips)
     extern struct {
         flags: usize,
-        sigaction: ?extern fn (i32, *siginfo_t, ?*c_void) void,
+        sigaction: ?fn (i32, *siginfo_t, ?*c_void) callconv(.C) void,
         mask: [4]u32,
-        restorer: extern fn () void,
+        restorer: fn () callconv(.C) void,
     }
 else
     extern struct {
-        sigaction: ?extern fn (i32, *siginfo_t, ?*c_void) void,
+        sigaction: ?fn (i32, *siginfo_t, ?*c_void) callconv(.C) void,
         flags: usize,
-        restorer: extern fn () void,
+        restorer: fn () callconv(.C) void,
         mask: [2]u32,
     };
 
@@ -831,7 +831,7 @@ pub const Sigaction = extern struct {
     sigaction: ?sigaction_fn,
     mask: sigset_t,
     flags: u32,
-    restorer: ?extern fn () void = null,
+    restorer: ?fn () callconv(.C) void = null,
 };
 
 pub const SIG_ERR = @intToPtr(?Sigaction.sigaction_fn, maxInt(usize));
diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index 15f9bf9b62..6653293e59 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -599,7 +599,7 @@ pub fn flock(fd: fd_t, operation: i32) usize {
 var vdso_clock_gettime = @ptrCast(?*const c_void, init_vdso_clock_gettime);
 
 // We must follow the C calling convention when we call into the VDSO
-const vdso_clock_gettime_ty = extern fn (i32, *timespec) usize;
+const vdso_clock_gettime_ty = fn (i32, *timespec) callconv(.C) usize;
 
 pub fn clock_gettime(clk_id: i32, tp: *timespec) usize {
     if (@hasDecl(@This(), "VDSO_CGT_SYM")) {
@@ -791,7 +791,7 @@ pub fn sigaction(sig: u6, noalias act: *const Sigaction, noalias oact: ?*Sigacti
         .sigaction = act.sigaction,
         .flags = act.flags | SA_RESTORER,
         .mask = undefined,
-        .restorer = @ptrCast(extern fn () void, restorer_fn),
+        .restorer = @ptrCast(fn () callconv(.C) void, restorer_fn),
     };
     var ksa_old: k_sigaction = undefined;
     const ksa_mask_size = @sizeOf(@TypeOf(ksa_old.mask));
diff --git a/lib/std/os/linux/arm-eabi.zig b/lib/std/os/linux/arm-eabi.zig
index c052aeab4e..352afeeb04 100644
--- a/lib/std/os/linux/arm-eabi.zig
+++ b/lib/std/os/linux/arm-eabi.zig
@@ -86,7 +86,7 @@ pub fn syscall6(
 }
 
 /// This matches the libc clone function.
-pub extern fn clone(func: extern fn (arg: usize) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
+pub extern fn clone(func: fn (arg: usize) callconv(.C) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
 
 pub fn restore() callconv(.Naked) void {
     return asm volatile ("svc #0"
diff --git a/lib/std/os/linux/arm64.zig b/lib/std/os/linux/arm64.zig
index 52ab3656e0..49548522ec 100644
--- a/lib/std/os/linux/arm64.zig
+++ b/lib/std/os/linux/arm64.zig
@@ -86,7 +86,7 @@ pub fn syscall6(
 }
 
 /// This matches the libc clone function.
-pub extern fn clone(func: extern fn (arg: usize) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
+pub extern fn clone(func: fn (arg: usize) callconv(.C) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
 
 pub const restore = restore_rt;
 
diff --git a/lib/std/os/linux/i386.zig b/lib/std/os/linux/i386.zig
index 0342f0754e..a4fdf8a346 100644
--- a/lib/std/os/linux/i386.zig
+++ b/lib/std/os/linux/i386.zig
@@ -106,7 +106,7 @@ pub fn socketcall(call: usize, args: [*]usize) usize {
 }
 
 /// This matches the libc clone function.
-pub extern fn clone(func: extern fn (arg: usize) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
+pub extern fn clone(func: fn (arg: usize) callconv(.C) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
 
 pub fn restore() callconv(.Naked) void {
     return asm volatile ("int $0x80"
diff --git a/lib/std/os/linux/mips.zig b/lib/std/os/linux/mips.zig
index 87c55db9f6..5b5c1e1f34 100644
--- a/lib/std/os/linux/mips.zig
+++ b/lib/std/os/linux/mips.zig
@@ -142,7 +142,7 @@ pub fn syscall6(
 }
 
 /// This matches the libc clone function.
-pub extern fn clone(func: extern fn (arg: usize) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
+pub extern fn clone(func: fn (arg: usize) callconv(.C) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
 
 pub fn restore() callconv(.Naked) void {
     return asm volatile ("syscall"
diff --git a/lib/std/os/linux/riscv64.zig b/lib/std/os/linux/riscv64.zig
index 3832bfbcca..39cc13f5b6 100644
--- a/lib/std/os/linux/riscv64.zig
+++ b/lib/std/os/linux/riscv64.zig
@@ -85,7 +85,7 @@ pub fn syscall6(
     );
 }
 
-pub extern fn clone(func: extern fn (arg: usize) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
+pub extern fn clone(func: fn (arg: usize) callconv(.C) u8, stack: usize, flags: u32, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
 
 pub const restore = restore_rt;
 
diff --git a/lib/std/os/linux/x86_64.zig b/lib/std/os/linux/x86_64.zig
index b60dcd80e9..33d2b66670 100644
--- a/lib/std/os/linux/x86_64.zig
+++ b/lib/std/os/linux/x86_64.zig
@@ -86,7 +86,7 @@ pub fn syscall6(
 }
 
 /// This matches the libc clone function.
-pub extern fn clone(func: extern fn (arg: usize) u8, stack: usize, flags: usize, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
+pub extern fn clone(func: fn (arg: usize) callconv(.C) u8, stack: usize, flags: usize, arg: usize, ptid: *i32, tls: usize, ctid: *i32) usize;
 
 pub const restore = restore_rt;
 
diff --git a/lib/std/os/uefi/protocols/absolute_pointer_protocol.zig b/lib/std/os/uefi/protocols/absolute_pointer_protocol.zig
index 1a46b9cf2c..a06a19c1a4 100644
--- a/lib/std/os/uefi/protocols/absolute_pointer_protocol.zig
+++ b/lib/std/os/uefi/protocols/absolute_pointer_protocol.zig
@@ -5,8 +5,8 @@ const Status = uefi.Status;
 
 /// Protocol for touchscreens
 pub const AbsolutePointerProtocol = extern struct {
-    _reset: extern fn (*const AbsolutePointerProtocol, bool) Status,
-    _get_state: extern fn (*const AbsolutePointerProtocol, *AbsolutePointerState) Status,
+    _reset: fn (*const AbsolutePointerProtocol, bool) callconv(.C) Status,
+    _get_state: fn (*const AbsolutePointerProtocol, *AbsolutePointerState) callconv(.C) Status,
     wait_for_input: Event,
     mode: *AbsolutePointerMode,
 
diff --git a/lib/std/os/uefi/protocols/edid_override_protocol.zig b/lib/std/os/uefi/protocols/edid_override_protocol.zig
index 2c37baa7a4..efe73982e9 100644
--- a/lib/std/os/uefi/protocols/edid_override_protocol.zig
+++ b/lib/std/os/uefi/protocols/edid_override_protocol.zig
@@ -5,7 +5,7 @@ const Status = uefi.Status;
 
 /// Override EDID information
 pub const EdidOverrideProtocol = extern struct {
-    _get_edid: extern fn (*const EdidOverrideProtocol, Handle, *u32, *usize, *?[*]u8) Status,
+    _get_edid: fn (*const EdidOverrideProtocol, Handle, *u32, *usize, *?[*]u8) callconv(.C) Status,
 
     /// Returns policy information and potentially a replacement EDID for the specified video output device.
     /// attributes must be align(4)
diff --git a/lib/std/os/uefi/protocols/file_protocol.zig b/lib/std/os/uefi/protocols/file_protocol.zig
index 4331d9a38c..eacd777008 100644
--- a/lib/std/os/uefi/protocols/file_protocol.zig
+++ b/lib/std/os/uefi/protocols/file_protocol.zig
@@ -5,16 +5,16 @@ const Status = uefi.Status;
 
 pub const FileProtocol = extern struct {
     revision: u64,
-    _open: extern fn (*const FileProtocol, **const FileProtocol, [*:0]const u16, u64, u64) Status,
-    _close: extern fn (*const FileProtocol) Status,
-    _delete: extern fn (*const FileProtocol) Status,
-    _read: extern fn (*const FileProtocol, *usize, [*]u8) Status,
-    _write: extern fn (*const FileProtocol, *usize, [*]const u8) Status,
-    _get_position: extern fn (*const FileProtocol, *u64) Status,
-    _set_position: extern fn (*const FileProtocol, *const u64) Status,
-    _get_info: extern fn (*const FileProtocol, *align(8) const Guid, *const usize, [*]u8) Status,
-    _set_info: extern fn (*const FileProtocol, *align(8) const Guid, usize, [*]const u8) Status,
-    _flush: extern fn (*const FileProtocol) Status,
+    _open: fn (*const FileProtocol, **const FileProtocol, [*:0]const u16, u64, u64) callconv(.C) Status,
+    _close: fn (*const FileProtocol) callconv(.C) Status,
+    _delete: fn (*const FileProtocol) callconv(.C) Status,
+    _read: fn (*const FileProtocol, *usize, [*]u8) callconv(.C) Status,
+    _write: fn (*const FileProtocol, *usize, [*]const u8) callconv(.C) Status,
+    _get_position: fn (*const FileProtocol, *u64) callconv(.C) Status,
+    _set_position: fn (*const FileProtocol, *const u64) callconv(.C) Status,
+    _get_info: fn (*const FileProtocol, *align(8) const Guid, *const usize, [*]u8) callconv(.C) Status,
+    _set_info: fn (*const FileProtocol, *align(8) const Guid, usize, [*]const u8) callconv(.C) Status,
+    _flush: fn (*const FileProtocol) callconv(.C) Status,
 
     pub fn open(self: *const FileProtocol, new_handle: **const FileProtocol, file_name: [*:0]const u16, open_mode: u64, attributes: u64) Status {
         return self._open(self, new_handle, file_name, open_mode, attributes);
diff --git a/lib/std/os/uefi/protocols/graphics_output_protocol.zig b/lib/std/os/uefi/protocols/graphics_output_protocol.zig
index 7370f537bf..1ceccce0bf 100644
--- a/lib/std/os/uefi/protocols/graphics_output_protocol.zig
+++ b/lib/std/os/uefi/protocols/graphics_output_protocol.zig
@@ -4,9 +4,9 @@ const Status = uefi.Status;
 
 /// Graphics output
 pub const GraphicsOutputProtocol = extern struct {
-    _query_mode: extern fn (*const GraphicsOutputProtocol, u32, *usize, **GraphicsOutputModeInformation) Status,
-    _set_mode: extern fn (*const GraphicsOutputProtocol, u32) Status,
-    _blt: extern fn (*const GraphicsOutputProtocol, ?[*]GraphicsOutputBltPixel, GraphicsOutputBltOperation, usize, usize, usize, usize, usize, usize, usize) Status,
+    _query_mode: fn (*const GraphicsOutputProtocol, u32, *usize, **GraphicsOutputModeInformation) callconv(.C) Status,
+    _set_mode: fn (*const GraphicsOutputProtocol, u32) callconv(.C) Status,
+    _blt: fn (*const GraphicsOutputProtocol, ?[*]GraphicsOutputBltPixel, GraphicsOutputBltOperation, usize, usize, usize, usize, usize, usize, usize) callconv(.C) Status,
     mode: *GraphicsOutputProtocolMode,
 
     /// Returns information for an available graphics mode that the graphics device and the set of active video output devices supports.
diff --git a/lib/std/os/uefi/protocols/hii_database_protocol.zig b/lib/std/os/uefi/protocols/hii_database_protocol.zig
index c79f693f6f..e34f72c2f3 100644
--- a/lib/std/os/uefi/protocols/hii_database_protocol.zig
+++ b/lib/std/os/uefi/protocols/hii_database_protocol.zig
@@ -6,10 +6,10 @@ const hii = uefi.protocols.hii;
 /// Database manager for HII-related data structures.
 pub const HIIDatabaseProtocol = extern struct {
     _new_package_list: Status, // TODO
-    _remove_package_list: extern fn (*const HIIDatabaseProtocol, hii.HIIHandle) Status,
-    _update_package_list: extern fn (*const HIIDatabaseProtocol, hii.HIIHandle, *const hii.HIIPackageList) Status,
-    _list_package_lists: extern fn (*const HIIDatabaseProtocol, u8, ?*const Guid, *usize, [*]hii.HIIHandle) Status,
-    _export_package_lists: extern fn (*const HIIDatabaseProtocol, ?hii.HIIHandle, *usize, *hii.HIIPackageList) Status,
+    _remove_package_list: fn (*const HIIDatabaseProtocol, hii.HIIHandle) callconv(.C) Status,
+    _update_package_list: fn (*const HIIDatabaseProtocol, hii.HIIHandle, *const hii.HIIPackageList) callconv(.C) Status,
+    _list_package_lists: fn (*const HIIDatabaseProtocol, u8, ?*const Guid, *usize, [*]hii.HIIHandle) callconv(.C) Status,
+    _export_package_lists: fn (*const HIIDatabaseProtocol, ?hii.HIIHandle, *usize, *hii.HIIPackageList) callconv(.C) Status,
     _register_package_notify: Status, // TODO
     _unregister_package_notify: Status, // TODO
     _find_keyboard_layouts: Status, // TODO
diff --git a/lib/std/os/uefi/protocols/hii_popup_protocol.zig b/lib/std/os/uefi/protocols/hii_popup_protocol.zig
index 96afe21fbc..2e4f621b41 100644
--- a/lib/std/os/uefi/protocols/hii_popup_protocol.zig
+++ b/lib/std/os/uefi/protocols/hii_popup_protocol.zig
@@ -6,7 +6,7 @@ const hii = uefi.protocols.hii;
 /// Display a popup window
 pub const HIIPopupProtocol = extern struct {
     revision: u64,
-    _create_popup: extern fn (*const HIIPopupProtocol, HIIPopupStyle, HIIPopupType, hii.HIIHandle, u16, ?*HIIPopupSelection) Status,
+    _create_popup: fn (*const HIIPopupProtocol, HIIPopupStyle, HIIPopupType, hii.HIIHandle, u16, ?*HIIPopupSelection) callconv(.C) Status,
 
     /// Displays a popup window.
     pub fn createPopup(self: *const HIIPopupProtocol, style: HIIPopupStyle, popup_type: HIIPopupType, handle: hii.HIIHandle, msg: u16, user_selection: ?*HIIPopupSelection) Status {
diff --git a/lib/std/os/uefi/protocols/ip6_config_protocol.zig b/lib/std/os/uefi/protocols/ip6_config_protocol.zig
index 89ff39e8d1..99ba76aa17 100644
--- a/lib/std/os/uefi/protocols/ip6_config_protocol.zig
+++ b/lib/std/os/uefi/protocols/ip6_config_protocol.zig
@@ -4,10 +4,10 @@ const Event = uefi.Event;
 const Status = uefi.Status;
 
 pub const Ip6ConfigProtocol = extern struct {
-    _set_data: extern fn (*const Ip6ConfigProtocol, Ip6ConfigDataType, usize, *const c_void) Status,
-    _get_data: extern fn (*const Ip6ConfigProtocol, Ip6ConfigDataType, *usize, ?*const c_void) Status,
-    _register_data_notify: extern fn (*const Ip6ConfigProtocol, Ip6ConfigDataType, Event) Status,
-    _unregister_data_notify: extern fn (*const Ip6ConfigProtocol, Ip6ConfigDataType, Event) Status,
+    _set_data: fn (*const Ip6ConfigProtocol, Ip6ConfigDataType, usize, *const c_void) callconv(.C) Status,
+    _get_data: fn (*const Ip6ConfigProtocol, Ip6ConfigDataType, *usize, ?*const c_void) callconv(.C) Status,
+    _register_data_notify: fn (*const Ip6ConfigProtocol, Ip6ConfigDataType, Event) callconv(.C) Status,
+    _unregister_data_notify: fn (*const Ip6ConfigProtocol, Ip6ConfigDataType, Event) callconv(.C) Status,
 
     pub fn setData(self: *const Ip6ConfigProtocol, data_type: Ip6ConfigDataType, data_size: usize, data: *const c_void) Status {
         return self._set_data(self, data_type, data_size, data);
diff --git a/lib/std/os/uefi/protocols/ip6_protocol.zig b/lib/std/os/uefi/protocols/ip6_protocol.zig
index f9a5c23d3c..b39ae60b2a 100644
--- a/lib/std/os/uefi/protocols/ip6_protocol.zig
+++ b/lib/std/os/uefi/protocols/ip6_protocol.zig
@@ -7,15 +7,15 @@ const ManagedNetworkConfigData = uefi.protocols.ManagedNetworkConfigData;
 const SimpleNetworkMode = uefi.protocols.SimpleNetworkMode;
 
 pub const Ip6Protocol = extern struct {
-    _get_mode_data: extern fn (*const Ip6Protocol, ?*Ip6ModeData, ?*ManagedNetworkConfigData, ?*SimpleNetworkMode) Status,
-    _configure: extern fn (*const Ip6Protocol, ?*const Ip6ConfigData) Status,
-    _groups: extern fn (*const Ip6Protocol, bool, ?*const Ip6Address) Status,
-    _routes: extern fn (*const Ip6Protocol, bool, ?*const Ip6Address, u8, ?*const Ip6Address) Status,
-    _neighbors: extern fn (*const Ip6Protocol, bool, *const Ip6Address, ?*const MacAddress, u32, bool) Status,
-    _transmit: extern fn (*const Ip6Protocol, *Ip6CompletionToken) Status,
-    _receive: extern fn (*const Ip6Protocol, *Ip6CompletionToken) Status,
-    _cancel: extern fn (*const Ip6Protocol, ?*Ip6CompletionToken) Status,
-    _poll: extern fn (*const Ip6Protocol) Status,
+    _get_mode_data: fn (*const Ip6Protocol, ?*Ip6ModeData, ?*ManagedNetworkConfigData, ?*SimpleNetworkMode) callconv(.C) Status,
+    _configure: fn (*const Ip6Protocol, ?*const Ip6ConfigData) callconv(.C) Status,
+    _groups: fn (*const Ip6Protocol, bool, ?*const Ip6Address) callconv(.C) Status,
+    _routes: fn (*const Ip6Protocol, bool, ?*const Ip6Address, u8, ?*const Ip6Address) callconv(.C) Status,
+    _neighbors: fn (*const Ip6Protocol, bool, *const Ip6Address, ?*const MacAddress, u32, bool) callconv(.C) Status,
+    _transmit: fn (*const Ip6Protocol, *Ip6CompletionToken) callconv(.C) Status,
+    _receive: fn (*const Ip6Protocol, *Ip6CompletionToken) callconv(.C) Status,
+    _cancel: fn (*const Ip6Protocol, ?*Ip6CompletionToken) callconv(.C) Status,
+    _poll: fn (*const Ip6Protocol) callconv(.C) Status,
 
     /// Gets the current operational settings for this instance of the EFI IPv6 Protocol driver.
     pub fn getModeData(self: *const Ip6Protocol, ip6_mode_data: ?*Ip6ModeData, mnp_config_data: ?*ManagedNetworkConfigData, snp_mode_data: ?*SimpleNetworkMode) Status {
diff --git a/lib/std/os/uefi/protocols/ip6_service_binding_protocol.zig b/lib/std/os/uefi/protocols/ip6_service_binding_protocol.zig
index 030ae5cae2..97ab1a431c 100644
--- a/lib/std/os/uefi/protocols/ip6_service_binding_protocol.zig
+++ b/lib/std/os/uefi/protocols/ip6_service_binding_protocol.zig
@@ -4,8 +4,8 @@ const Guid = uefi.Guid;
 const Status = uefi.Status;
 
 pub const Ip6ServiceBindingProtocol = extern struct {
-    _create_child: extern fn (*const Ip6ServiceBindingProtocol, *?Handle) Status,
-    _destroy_child: extern fn (*const Ip6ServiceBindingProtocol, Handle) Status,
+    _create_child: fn (*const Ip6ServiceBindingProtocol, *?Handle) callconv(.C) Status,
+    _destroy_child: fn (*const Ip6ServiceBindingProtocol, Handle) callconv(.C) Status,
 
     pub fn createChild(self: *const Ip6ServiceBindingProtocol, handle: *?Handle) Status {
         return self._create_child(self, handle);
diff --git a/lib/std/os/uefi/protocols/loaded_image_protocol.zig b/lib/std/os/uefi/protocols/loaded_image_protocol.zig
index cff2bdccc0..b8afcb1063 100644
--- a/lib/std/os/uefi/protocols/loaded_image_protocol.zig
+++ b/lib/std/os/uefi/protocols/loaded_image_protocol.zig
@@ -19,7 +19,7 @@ pub const LoadedImageProtocol = extern struct {
     image_size: u64,
     image_code_type: MemoryType,
     image_data_type: MemoryType,
-    _unload: extern fn (*const LoadedImageProtocol, Handle) Status,
+    _unload: fn (*const LoadedImageProtocol, Handle) callconv(.C) Status,
 
     /// Unloads an image from memory.
     pub fn unload(self: *const LoadedImageProtocol, handle: Handle) Status {
diff --git a/lib/std/os/uefi/protocols/managed_network_protocol.zig b/lib/std/os/uefi/protocols/managed_network_protocol.zig
index 60dc6996ad..34ef6c40fa 100644
--- a/lib/std/os/uefi/protocols/managed_network_protocol.zig
+++ b/lib/std/os/uefi/protocols/managed_network_protocol.zig
@@ -7,14 +7,14 @@ const SimpleNetworkMode = uefi.protocols.SimpleNetworkMode;
 const MacAddress = uefi.protocols.MacAddress;
 
 pub const ManagedNetworkProtocol = extern struct {
-    _get_mode_data: extern fn (*const ManagedNetworkProtocol, ?*ManagedNetworkConfigData, ?*SimpleNetworkMode) Status,
-    _configure: extern fn (*const ManagedNetworkProtocol, ?*const ManagedNetworkConfigData) Status,
-    _mcast_ip_to_mac: extern fn (*const ManagedNetworkProtocol, bool, *const c_void, *MacAddress) Status,
-    _groups: extern fn (*const ManagedNetworkProtocol, bool, ?*const MacAddress) Status,
-    _transmit: extern fn (*const ManagedNetworkProtocol, *const ManagedNetworkCompletionToken) Status,
-    _receive: extern fn (*const ManagedNetworkProtocol, *const ManagedNetworkCompletionToken) Status,
-    _cancel: extern fn (*const ManagedNetworkProtocol, ?*const ManagedNetworkCompletionToken) Status,
-    _poll: extern fn (*const ManagedNetworkProtocol) usize,
+    _get_mode_data: fn (*const ManagedNetworkProtocol, ?*ManagedNetworkConfigData, ?*SimpleNetworkMode) callconv(.C) Status,
+    _configure: fn (*const ManagedNetworkProtocol, ?*const ManagedNetworkConfigData) callconv(.C) Status,
+    _mcast_ip_to_mac: fn (*const ManagedNetworkProtocol, bool, *const c_void, *MacAddress) callconv(.C) Status,
+    _groups: fn (*const ManagedNetworkProtocol, bool, ?*const MacAddress) callconv(.C) Status,
+    _transmit: fn (*const ManagedNetworkProtocol, *const ManagedNetworkCompletionToken) callconv(.C) Status,
+    _receive: fn (*const ManagedNetworkProtocol, *const ManagedNetworkCompletionToken) callconv(.C) Status,
+    _cancel: fn (*const ManagedNetworkProtocol, ?*const ManagedNetworkCompletionToken) callconv(.C) Status,
+    _poll: fn (*const ManagedNetworkProtocol) callconv(.C) usize,
 
     /// Returns the operational parameters for the current MNP child driver.
     /// May also support returning the underlying SNP driver mode data.
diff --git a/lib/std/os/uefi/protocols/managed_network_service_binding_protocol.zig b/lib/std/os/uefi/protocols/managed_network_service_binding_protocol.zig
index ea8bd470c3..e9657e4456 100644
--- a/lib/std/os/uefi/protocols/managed_network_service_binding_protocol.zig
+++ b/lib/std/os/uefi/protocols/managed_network_service_binding_protocol.zig
@@ -4,8 +4,8 @@ const Guid = uefi.Guid;
 const Status = uefi.Status;
 
 pub const ManagedNetworkServiceBindingProtocol = extern struct {
-    _create_child: extern fn (*const ManagedNetworkServiceBindingProtocol, *?Handle) Status,
-    _destroy_child: extern fn (*const ManagedNetworkServiceBindingProtocol, Handle) Status,
+    _create_child: fn (*const ManagedNetworkServiceBindingProtocol, *?Handle) callconv(.C) Status,
+    _destroy_child: fn (*const ManagedNetworkServiceBindingProtocol, Handle) callconv(.C) Status,
 
     pub fn createChild(self: *const ManagedNetworkServiceBindingProtocol, handle: *?Handle) Status {
         return self._create_child(self, handle);
diff --git a/lib/std/os/uefi/protocols/rng_protocol.zig b/lib/std/os/uefi/protocols/rng_protocol.zig
index 4d5dd496af..a32b202f44 100644
--- a/lib/std/os/uefi/protocols/rng_protocol.zig
+++ b/lib/std/os/uefi/protocols/rng_protocol.zig
@@ -4,8 +4,8 @@ const Status = uefi.Status;
 
 /// Random Number Generator protocol
 pub const RNGProtocol = extern struct {
-    _get_info: extern fn (*const RNGProtocol, *usize, [*]align(8) Guid) Status,
-    _get_rng: extern fn (*const RNGProtocol, ?*align(8) const Guid, usize, [*]u8) Status,
+    _get_info: fn (*const RNGProtocol, *usize, [*]align(8) Guid) callconv(.C) Status,
+    _get_rng: fn (*const RNGProtocol, ?*align(8) const Guid, usize, [*]u8) callconv(.C) Status,
 
     /// Returns information about the random number generation implementation.
     pub fn getInfo(self: *const RNGProtocol, list_size: *usize, list: [*]align(8) Guid) Status {
diff --git a/lib/std/os/uefi/protocols/simple_file_system_protocol.zig b/lib/std/os/uefi/protocols/simple_file_system_protocol.zig
index 31da02595a..119c1e6587 100644
--- a/lib/std/os/uefi/protocols/simple_file_system_protocol.zig
+++ b/lib/std/os/uefi/protocols/simple_file_system_protocol.zig
@@ -5,7 +5,7 @@ const Status = uefi.Status;
 
 pub const SimpleFileSystemProtocol = extern struct {
     revision: u64,
-    _open_volume: extern fn (*const SimpleFileSystemProtocol, **const FileProtocol) Status,
+    _open_volume: fn (*const SimpleFileSystemProtocol, **const FileProtocol) callconv(.C) Status,
 
     pub fn openVolume(self: *const SimpleFileSystemProtocol, root: **const FileProtocol) Status {
         return self._open_volume(self, root);
diff --git a/lib/std/os/uefi/protocols/simple_network_protocol.zig b/lib/std/os/uefi/protocols/simple_network_protocol.zig
index a0d85b06d1..ac7446036e 100644
--- a/lib/std/os/uefi/protocols/simple_network_protocol.zig
+++ b/lib/std/os/uefi/protocols/simple_network_protocol.zig
@@ -5,19 +5,19 @@ const Status = uefi.Status;
 
 pub const SimpleNetworkProtocol = extern struct {
     revision: u64,
-    _start: extern fn (*const SimpleNetworkProtocol) Status,
-    _stop: extern fn (*const SimpleNetworkProtocol) Status,
-    _initialize: extern fn (*const SimpleNetworkProtocol, usize, usize) Status,
-    _reset: extern fn (*const SimpleNetworkProtocol, bool) Status,
-    _shutdown: extern fn (*const SimpleNetworkProtocol) Status,
-    _receive_filters: extern fn (*const SimpleNetworkProtocol, SimpleNetworkReceiveFilter, SimpleNetworkReceiveFilter, bool, usize, ?[*]const MacAddress) Status,
-    _station_address: extern fn (*const SimpleNetworkProtocol, bool, ?*const MacAddress) Status,
-    _statistics: extern fn (*const SimpleNetworkProtocol, bool, ?*usize, ?*NetworkStatistics) Status,
-    _mcast_ip_to_mac: extern fn (*const SimpleNetworkProtocol, bool, *const c_void, *MacAddress) Status,
-    _nvdata: extern fn (*const SimpleNetworkProtocol, bool, usize, usize, [*]u8) Status,
-    _get_status: extern fn (*const SimpleNetworkProtocol, *SimpleNetworkInterruptStatus, ?*?[*]u8) Status,
-    _transmit: extern fn (*const SimpleNetworkProtocol, usize, usize, [*]const u8, ?*const MacAddress, ?*const MacAddress, ?*const u16) Status,
-    _receive: extern fn (*const SimpleNetworkProtocol, ?*usize, *usize, [*]u8, ?*MacAddress, ?*MacAddress, ?*u16) Status,
+    _start: fn (*const SimpleNetworkProtocol) callconv(.C) Status,
+    _stop: fn (*const SimpleNetworkProtocol) callconv(.C) Status,
+    _initialize: fn (*const SimpleNetworkProtocol, usize, usize) callconv(.C) Status,
+    _reset: fn (*const SimpleNetworkProtocol, bool) callconv(.C) Status,
+    _shutdown: fn (*const SimpleNetworkProtocol) callconv(.C) Status,
+    _receive_filters: fn (*const SimpleNetworkProtocol, SimpleNetworkReceiveFilter, SimpleNetworkReceiveFilter, bool, usize, ?[*]const MacAddress) callconv(.C) Status,
+    _station_address: fn (*const SimpleNetworkProtocol, bool, ?*const MacAddress) callconv(.C) Status,
+    _statistics: fn (*const SimpleNetworkProtocol, bool, ?*usize, ?*NetworkStatistics) callconv(.C) Status,
+    _mcast_ip_to_mac: fn (*const SimpleNetworkProtocol, bool, *const c_void, *MacAddress) callconv(.C) Status,
+    _nvdata: fn (*const SimpleNetworkProtocol, bool, usize, usize, [*]u8) callconv(.C) Status,
+    _get_status: fn (*const SimpleNetworkProtocol, *SimpleNetworkInterruptStatus, ?*?[*]u8) callconv(.C) Status,
+    _transmit: fn (*const SimpleNetworkProtocol, usize, usize, [*]const u8, ?*const MacAddress, ?*const MacAddress, ?*const u16) callconv(.C) Status,
+    _receive: fn (*const SimpleNetworkProtocol, ?*usize, *usize, [*]u8, ?*MacAddress, ?*MacAddress, ?*u16) callconv(.C) Status,
     wait_for_packet: Event,
     mode: *SimpleNetworkMode,
 
diff --git a/lib/std/os/uefi/protocols/simple_pointer_protocol.zig b/lib/std/os/uefi/protocols/simple_pointer_protocol.zig
index 2d1c7d4504..d217ab5930 100644
--- a/lib/std/os/uefi/protocols/simple_pointer_protocol.zig
+++ b/lib/std/os/uefi/protocols/simple_pointer_protocol.zig
@@ -5,8 +5,8 @@ const Status = uefi.Status;
 
 /// Protocol for mice
 pub const SimplePointerProtocol = struct {
-    _reset: extern fn (*const SimplePointerProtocol, bool) Status,
-    _get_state: extern fn (*const SimplePointerProtocol, *SimplePointerState) Status,
+    _reset: fn (*const SimplePointerProtocol, bool) callconv(.C) Status,
+    _get_state: fn (*const SimplePointerProtocol, *SimplePointerState) callconv(.C) Status,
     wait_for_input: Event,
     mode: *SimplePointerMode,
 
diff --git a/lib/std/os/uefi/protocols/simple_text_input_ex_protocol.zig b/lib/std/os/uefi/protocols/simple_text_input_ex_protocol.zig
index c361ffa9a1..4a2b098e61 100644
--- a/lib/std/os/uefi/protocols/simple_text_input_ex_protocol.zig
+++ b/lib/std/os/uefi/protocols/simple_text_input_ex_protocol.zig
@@ -5,12 +5,12 @@ const Status = uefi.Status;
 
 /// Character input devices, e.g. Keyboard
 pub const SimpleTextInputExProtocol = extern struct {
-    _reset: extern fn (*const SimpleTextInputExProtocol, bool) Status,
-    _read_key_stroke_ex: extern fn (*const SimpleTextInputExProtocol, *KeyData) Status,
+    _reset: fn (*const SimpleTextInputExProtocol, bool) callconv(.C) Status,
+    _read_key_stroke_ex: fn (*const SimpleTextInputExProtocol, *KeyData) callconv(.C) Status,
     wait_for_key_ex: Event,
-    _set_state: extern fn (*const SimpleTextInputExProtocol, *const u8) Status,
-    _register_key_notify: extern fn (*const SimpleTextInputExProtocol, *const KeyData, extern fn (*const KeyData) usize, **c_void) Status,
-    _unregister_key_notify: extern fn (*const SimpleTextInputExProtocol, *const c_void) Status,
+    _set_state: fn (*const SimpleTextInputExProtocol, *const u8) callconv(.C) Status,
+    _register_key_notify: fn (*const SimpleTextInputExProtocol, *const KeyData, fn (*const KeyData) callconv(.C) usize, **c_void) callconv(.C) Status,
+    _unregister_key_notify: fn (*const SimpleTextInputExProtocol, *const c_void) callconv(.C) Status,
 
     /// Resets the input device hardware.
     pub fn reset(self: *const SimpleTextInputExProtocol, verify: bool) Status {
@@ -28,7 +28,7 @@ pub const SimpleTextInputExProtocol = extern struct {
     }
 
     /// Register a notification function for a particular keystroke for the input device.
-    pub fn registerKeyNotify(self: *const SimpleTextInputExProtocol, key_data: *const KeyData, notify: extern fn (*const KeyData) usize, handle: **c_void) Status {
+    pub fn registerKeyNotify(self: *const SimpleTextInputExProtocol, key_data: *const KeyData, notify: fn (*const KeyData) callconv(.C) usize, handle: **c_void) Status {
         return self._register_key_notify(self, key_data, notify, handle);
     }
 
diff --git a/lib/std/os/uefi/protocols/simple_text_input_protocol.zig b/lib/std/os/uefi/protocols/simple_text_input_protocol.zig
index fdae001145..58ed071331 100644
--- a/lib/std/os/uefi/protocols/simple_text_input_protocol.zig
+++ b/lib/std/os/uefi/protocols/simple_text_input_protocol.zig
@@ -6,8 +6,8 @@ const Status = uefi.Status;
 
 /// Character input devices, e.g. Keyboard
 pub const SimpleTextInputProtocol = extern struct {
-    _reset: extern fn (*const SimpleTextInputProtocol, bool) usize,
-    _read_key_stroke: extern fn (*const SimpleTextInputProtocol, *InputKey) Status,
+    _reset: fn (*const SimpleTextInputProtocol, bool) callconv(.C) usize,
+    _read_key_stroke: fn (*const SimpleTextInputProtocol, *InputKey) callconv(.C) Status,
     wait_for_key: Event,
 
     /// Resets the input device hardware.
diff --git a/lib/std/os/uefi/protocols/simple_text_output_protocol.zig b/lib/std/os/uefi/protocols/simple_text_output_protocol.zig
index 09f3cb1cd2..84f540cb78 100644
--- a/lib/std/os/uefi/protocols/simple_text_output_protocol.zig
+++ b/lib/std/os/uefi/protocols/simple_text_output_protocol.zig
@@ -4,15 +4,15 @@ const Status = uefi.Status;
 
 /// Character output devices
 pub const SimpleTextOutputProtocol = extern struct {
-    _reset: extern fn (*const SimpleTextOutputProtocol, bool) Status,
-    _output_string: extern fn (*const SimpleTextOutputProtocol, [*:0]const u16) Status,
-    _test_string: extern fn (*const SimpleTextOutputProtocol, [*:0]const u16) Status,
-    _query_mode: extern fn (*const SimpleTextOutputProtocol, usize, *usize, *usize) Status,
-    _set_mode: extern fn (*const SimpleTextOutputProtocol, usize) Status,
-    _set_attribute: extern fn (*const SimpleTextOutputProtocol, usize) Status,
-    _clear_screen: extern fn (*const SimpleTextOutputProtocol) Status,
-    _set_cursor_position: extern fn (*const SimpleTextOutputProtocol, usize, usize) Status,
-    _enable_cursor: extern fn (*const SimpleTextOutputProtocol, bool) Status,
+    _reset: fn (*const SimpleTextOutputProtocol, bool) callconv(.C) Status,
+    _output_string: fn (*const SimpleTextOutputProtocol, [*:0]const u16) callconv(.C) Status,
+    _test_string: fn (*const SimpleTextOutputProtocol, [*:0]const u16) callconv(.C) Status,
+    _query_mode: fn (*const SimpleTextOutputProtocol, usize, *usize, *usize) callconv(.C) Status,
+    _set_mode: fn (*const SimpleTextOutputProtocol, usize) callconv(.C) Status,
+    _set_attribute: fn (*const SimpleTextOutputProtocol, usize) callconv(.C) Status,
+    _clear_screen: fn (*const SimpleTextOutputProtocol) callconv(.C) Status,
+    _set_cursor_position: fn (*const SimpleTextOutputProtocol, usize, usize) callconv(.C) Status,
+    _enable_cursor: fn (*const SimpleTextOutputProtocol, bool) callconv(.C) Status,
     mode: *SimpleTextOutputMode,
 
     /// Resets the text output device hardware.
diff --git a/lib/std/os/uefi/protocols/udp6_protocol.zig b/lib/std/os/uefi/protocols/udp6_protocol.zig
index f0ab2789f3..46c76beaa6 100644
--- a/lib/std/os/uefi/protocols/udp6_protocol.zig
+++ b/lib/std/os/uefi/protocols/udp6_protocol.zig
@@ -9,13 +9,13 @@ const ManagedNetworkConfigData = uefi.protocols.ManagedNetworkConfigData;
 const SimpleNetworkMode = uefi.protocols.SimpleNetworkMode;
 
 pub const Udp6Protocol = extern struct {
-    _get_mode_data: extern fn (*const Udp6Protocol, ?*Udp6ConfigData, ?*Ip6ModeData, ?*ManagedNetworkConfigData, ?*SimpleNetworkMode) Status,
-    _configure: extern fn (*const Udp6Protocol, ?*const Udp6ConfigData) Status,
-    _groups: extern fn (*const Udp6Protocol, bool, ?*const Ip6Address) Status,
-    _transmit: extern fn (*const Udp6Protocol, *Udp6CompletionToken) Status,
-    _receive: extern fn (*const Udp6Protocol, *Udp6CompletionToken) Status,
-    _cancel: extern fn (*const Udp6Protocol, ?*Udp6CompletionToken) Status,
-    _poll: extern fn (*const Udp6Protocol) Status,
+    _get_mode_data: fn (*const Udp6Protocol, ?*Udp6ConfigData, ?*Ip6ModeData, ?*ManagedNetworkConfigData, ?*SimpleNetworkMode) callconv(.C) Status,
+    _configure: fn (*const Udp6Protocol, ?*const Udp6ConfigData) callconv(.C) Status,
+    _groups: fn (*const Udp6Protocol, bool, ?*const Ip6Address) callconv(.C) Status,
+    _transmit: fn (*const Udp6Protocol, *Udp6CompletionToken) callconv(.C) Status,
+    _receive: fn (*const Udp6Protocol, *Udp6CompletionToken) callconv(.C) Status,
+    _cancel: fn (*const Udp6Protocol, ?*Udp6CompletionToken) callconv(.C) Status,
+    _poll: fn (*const Udp6Protocol) callconv(.C) Status,
 
     pub fn getModeData(self: *const Udp6Protocol, udp6_config_data: ?*Udp6ConfigData, ip6_mode_data: ?*Ip6ModeData, mnp_config_data: ?*ManagedNetworkConfigData, snp_mode_data: ?*SimpleNetworkMode) Status {
         return self._get_mode_data(self, udp6_config_data, ip6_mode_data, mnp_config_data, snp_mode_data);
diff --git a/lib/std/os/uefi/protocols/udp6_service_binding_protocol.zig b/lib/std/os/uefi/protocols/udp6_service_binding_protocol.zig
index 9a7a67807c..811692adc3 100644
--- a/lib/std/os/uefi/protocols/udp6_service_binding_protocol.zig
+++ b/lib/std/os/uefi/protocols/udp6_service_binding_protocol.zig
@@ -4,8 +4,8 @@ const Guid = uefi.Guid;
 const Status = uefi.Status;
 
 pub const Udp6ServiceBindingProtocol = extern struct {
-    _create_child: extern fn (*const Udp6ServiceBindingProtocol, *?Handle) Status,
-    _destroy_child: extern fn (*const Udp6ServiceBindingProtocol, Handle) Status,
+    _create_child: fn (*const Udp6ServiceBindingProtocol, *?Handle) callconv(.C) Status,
+    _destroy_child: fn (*const Udp6ServiceBindingProtocol, Handle) callconv(.C) Status,
 
     pub fn createChild(self: *const Udp6ServiceBindingProtocol, handle: *?Handle) Status {
         return self._create_child(self, handle);
diff --git a/lib/std/os/uefi/tables/boot_services.zig b/lib/std/os/uefi/tables/boot_services.zig
index 1969b46403..a1d2c1ca59 100644
--- a/lib/std/os/uefi/tables/boot_services.zig
+++ b/lib/std/os/uefi/tables/boot_services.zig
@@ -21,117 +21,117 @@ pub const BootServices = extern struct {
     hdr: TableHeader,
 
     /// Raises a task's priority level and returns its previous level.
-    raiseTpl: extern fn (usize) usize,
+    raiseTpl: fn (usize) callconv(.C) usize,
 
     /// Restores a task's priority level to its previous value.
-    restoreTpl: extern fn (usize) void,
+    restoreTpl: fn (usize) callconv(.C) void,
 
     /// Allocates memory pages from the system.
-    allocatePages: extern fn (AllocateType, MemoryType, usize, *[*]align(4096) u8) Status,
+    allocatePages: fn (AllocateType, MemoryType, usize, *[*]align(4096) u8) callconv(.C) Status,
 
     /// Frees memory pages.
-    freePages: extern fn ([*]align(4096) u8, usize) Status,
+    freePages: fn ([*]align(4096) u8, usize) callconv(.C) Status,
 
     /// Returns the current memory map.
-    getMemoryMap: extern fn (*usize, [*]MemoryDescriptor, *usize, *usize, *u32) Status,
+    getMemoryMap: fn (*usize, [*]MemoryDescriptor, *usize, *usize, *u32) callconv(.C) Status,
 
     /// Allocates pool memory.
-    allocatePool: extern fn (MemoryType, usize, *[*]align(8) u8) Status,
+    allocatePool: fn (MemoryType, usize, *[*]align(8) u8) callconv(.C) Status,
 
     /// Returns pool memory to the system.
-    freePool: extern fn ([*]align(8) u8) Status,
+    freePool: fn ([*]align(8) u8) callconv(.C) Status,
 
     /// Creates an event.
-    createEvent: extern fn (u32, usize, ?extern fn (Event, ?*c_void) void, ?*const c_void, *Event) Status,
+    createEvent: fn (u32, usize, ?fn (Event, ?*c_void) callconv(.C) void, ?*const c_void, *Event) callconv(.C) Status,
 
     /// Sets the type of timer and the trigger time for a timer event.
-    setTimer: extern fn (Event, TimerDelay, u64) Status,
+    setTimer: fn (Event, TimerDelay, u64) callconv(.C) Status,
 
     /// Stops execution until an event is signaled.
-    waitForEvent: extern fn (usize, [*]const Event, *usize) Status,
+    waitForEvent: fn (usize, [*]const Event, *usize) callconv(.C) Status,
 
     /// Signals an event.
-    signalEvent: extern fn (Event) Status,
+    signalEvent: fn (Event) callconv(.C) Status,
 
     /// Closes an event.
-    closeEvent: extern fn (Event) Status,
+    closeEvent: fn (Event) callconv(.C) Status,
 
     /// Checks whether an event is in the signaled state.
-    checkEvent: extern fn (Event) Status,
+    checkEvent: fn (Event) callconv(.C) Status,
 
     installProtocolInterface: Status, // TODO
     reinstallProtocolInterface: Status, // TODO
     uninstallProtocolInterface: Status, // TODO
 
     /// Queries a handle to determine if it supports a specified protocol.
-    handleProtocol: extern fn (Handle, *align(8) const Guid, *?*c_void) Status,
+    handleProtocol: fn (Handle, *align(8) const Guid, *?*c_void) callconv(.C) Status,
 
     reserved: *c_void,
 
     registerProtocolNotify: Status, // TODO
 
     /// Returns an array of handles that support a specified protocol.
-    locateHandle: extern fn (LocateSearchType, ?*align(8) const Guid, ?*const c_void, *usize, [*]Handle) Status,
+    locateHandle: fn (LocateSearchType, ?*align(8) const Guid, ?*const c_void, *usize, [*]Handle) callconv(.C) Status,
 
     locateDevicePath: Status, // TODO
     installConfigurationTable: Status, // TODO
 
     /// Loads an EFI image into memory.
-    loadImage: extern fn (bool, Handle, ?*const DevicePathProtocol, ?[*]const u8, usize, *?Handle) Status,
+    loadImage: fn (bool, Handle, ?*const DevicePathProtocol, ?[*]const u8, usize, *?Handle) callconv(.C) Status,
 
     /// Transfers control to a loaded image's entry point.
-    startImage: extern fn (Handle, ?*usize, ?*[*]u16) Status,
+    startImage: fn (Handle, ?*usize, ?*[*]u16) callconv(.C) Status,
 
     /// Terminates a loaded EFI image and returns control to boot services.
-    exit: extern fn (Handle, Status, usize, ?*const c_void) Status,
+    exit: fn (Handle, Status, usize, ?*const c_void) callconv(.C) Status,
 
     /// Unloads an image.
-    unloadImage: extern fn (Handle) Status,
+    unloadImage: fn (Handle) callconv(.C) Status,
 
     /// Terminates all boot services.
-    exitBootServices: extern fn (Handle, usize) Status,
+    exitBootServices: fn (Handle, usize) callconv(.C) Status,
 
     /// Returns a monotonically increasing count for the platform.
-    getNextMonotonicCount: extern fn (*u64) Status,
+    getNextMonotonicCount: fn (*u64) callconv(.C) Status,
 
     /// Induces a fine-grained stall.
-    stall: extern fn (usize) Status,
+    stall: fn (usize) callconv(.C) Status,
 
     /// Sets the system's watchdog timer.
-    setWatchdogTimer: extern fn (usize, u64, usize, ?[*]const u16) Status,
+    setWatchdogTimer: fn (usize, u64, usize, ?[*]const u16) callconv(.C) Status,
 
     connectController: Status, // TODO
     disconnectController: Status, // TODO
 
     /// Queries a handle to determine if it supports a specified protocol.
-    openProtocol: extern fn (Handle, *align(8) const Guid, *?*c_void, ?Handle, ?Handle, OpenProtocolAttributes) Status,
+    openProtocol: fn (Handle, *align(8) const Guid, *?*c_void, ?Handle, ?Handle, OpenProtocolAttributes) callconv(.C) Status,
 
     /// Closes a protocol on a handle that was opened using openProtocol().
-    closeProtocol: extern fn (Handle, *align(8) const Guid, Handle, ?Handle) Status,
+    closeProtocol: fn (Handle, *align(8) const Guid, Handle, ?Handle) callconv(.C) Status,
 
     /// Retrieves the list of agents that currently have a protocol interface opened.
-    openProtocolInformation: extern fn (Handle, *align(8) const Guid, *[*]ProtocolInformationEntry, *usize) Status,
+    openProtocolInformation: fn (Handle, *align(8) const Guid, *[*]ProtocolInformationEntry, *usize) callconv(.C) Status,
 
     /// Retrieves the list of protocol interface GUIDs that are installed on a handle in a buffer allocated from pool.
-    protocolsPerHandle: extern fn (Handle, *[*]*align(8) const Guid, *usize) Status,
+    protocolsPerHandle: fn (Handle, *[*]*align(8) const Guid, *usize) callconv(.C) Status,
 
     /// Returns an array of handles that support the requested protocol in a buffer allocated from pool.
-    locateHandleBuffer: extern fn (LocateSearchType, ?*align(8) const Guid, ?*const c_void, *usize, *[*]Handle) Status,
+    locateHandleBuffer: fn (LocateSearchType, ?*align(8) const Guid, ?*const c_void, *usize, *[*]Handle) callconv(.C) Status,
 
     /// Returns the first protocol instance that matches the given protocol.
-    locateProtocol: extern fn (*align(8) const Guid, ?*const c_void, *?*c_void) Status,
+    locateProtocol: fn (*align(8) const Guid, ?*const c_void, *?*c_void) callconv(.C) Status,
 
     installMultipleProtocolInterfaces: Status, // TODO
     uninstallMultipleProtocolInterfaces: Status, // TODO
 
     /// Computes and returns a 32-bit CRC for a data buffer.
-    calculateCrc32: extern fn ([*]const u8, usize, *u32) Status,
+    calculateCrc32: fn ([*]const u8, usize, *u32) callconv(.C) Status,
 
     /// Copies the contents of one buffer to another buffer
-    copyMem: extern fn ([*]u8, [*]const u8, usize) void,
+    copyMem: fn ([*]u8, [*]const u8, usize) callconv(.C) void,
 
     /// Fills a buffer with a specified value
-    setMem: extern fn ([*]u8, usize, u8) void,
+    setMem: fn ([*]u8, usize, u8) callconv(.C) void,
 
     createEventEx: Status, // TODO
 
diff --git a/lib/std/os/uefi/tables/runtime_services.zig b/lib/std/os/uefi/tables/runtime_services.zig
index 1f0c7efad4..981e07275b 100644
--- a/lib/std/os/uefi/tables/runtime_services.zig
+++ b/lib/std/os/uefi/tables/runtime_services.zig
@@ -17,7 +17,7 @@ pub const RuntimeServices = extern struct {
     hdr: TableHeader,
 
     /// Returns the current time and date information, and the time-keeping capabilities of the hardware platform.
-    getTime: extern fn (*uefi.Time, ?*TimeCapabilities) Status,
+    getTime: fn (*uefi.Time, ?*TimeCapabilities) callconv(.C) Status,
 
     setTime: Status, // TODO
     getWakeupTime: Status, // TODO
@@ -26,18 +26,18 @@ pub const RuntimeServices = extern struct {
     convertPointer: Status, // TODO
 
     /// Returns the value of a variable.
-    getVariable: extern fn ([*:0]const u16, *align(8) const Guid, ?*u32, *usize, ?*c_void) Status,
+    getVariable: fn ([*:0]const u16, *align(8) const Guid, ?*u32, *usize, ?*c_void) callconv(.C) Status,
 
     /// Enumerates the current variable names.
-    getNextVariableName: extern fn (*usize, [*:0]u16, *align(8) Guid) Status,
+    getNextVariableName: fn (*usize, [*:0]u16, *align(8) Guid) callconv(.C) Status,
 
     /// Sets the value of a variable.
-    setVariable: extern fn ([*:0]const u16, *align(8) const Guid, u32, usize, *c_void) Status,
+    setVariable: fn ([*:0]const u16, *align(8) const Guid, u32, usize, *c_void) callconv(.C) Status,
 
     getNextHighMonotonicCount: Status, // TODO
 
     /// Resets the entire platform.
-    resetSystem: extern fn (ResetType, Status, usize, ?*const c_void) noreturn,
+    resetSystem: fn (ResetType, Status, usize, ?*const c_void) callconv(.C) noreturn,
 
     updateCapsule: Status, // TODO
     queryCapsuleCapabilities: Status, // TODO
diff --git a/lib/std/os/windows/bits.zig b/lib/std/os/windows/bits.zig
index a1a60b1798..191e8deded 100644
--- a/lib/std/os/windows/bits.zig
+++ b/lib/std/os/windows/bits.zig
@@ -627,7 +627,7 @@ pub const MEM_RESERVE_PLACEHOLDERS = 0x2;
 pub const MEM_DECOMMIT = 0x4000;
 pub const MEM_RELEASE = 0x8000;
 
-pub const PTHREAD_START_ROUTINE = extern fn (LPVOID) DWORD;
+pub const PTHREAD_START_ROUTINE = fn (LPVOID) callconv(.C) DWORD;
 pub const LPTHREAD_START_ROUTINE = PTHREAD_START_ROUTINE;
 
 pub const WIN32_FIND_DATAW = extern struct {
@@ -784,7 +784,7 @@ pub const IMAGE_TLS_DIRECTORY = extern struct {
 pub const IMAGE_TLS_DIRECTORY64 = IMAGE_TLS_DIRECTORY;
 pub const IMAGE_TLS_DIRECTORY32 = IMAGE_TLS_DIRECTORY;
 
-pub const PIMAGE_TLS_CALLBACK = ?extern fn (PVOID, DWORD, PVOID) void;
+pub const PIMAGE_TLS_CALLBACK = ?fn (PVOID, DWORD, PVOID) callconv(.C) void;
 
 pub const PROV_RSA_FULL = 1;
 
@@ -810,7 +810,7 @@ pub const FILE_ACTION_MODIFIED = 0x00000003;
 pub const FILE_ACTION_RENAMED_OLD_NAME = 0x00000004;
 pub const FILE_ACTION_RENAMED_NEW_NAME = 0x00000005;
 
-pub const LPOVERLAPPED_COMPLETION_ROUTINE = ?extern fn (DWORD, DWORD, *OVERLAPPED) void;
+pub const LPOVERLAPPED_COMPLETION_ROUTINE = ?fn (DWORD, DWORD, *OVERLAPPED) callconv(.C) void;
 
 pub const FILE_NOTIFY_CHANGE_CREATION = 64;
 pub const FILE_NOTIFY_CHANGE_SIZE = 8;
@@ -863,7 +863,7 @@ pub const RTL_CRITICAL_SECTION = extern struct {
 pub const CRITICAL_SECTION = RTL_CRITICAL_SECTION;
 pub const INIT_ONCE = RTL_RUN_ONCE;
 pub const INIT_ONCE_STATIC_INIT = RTL_RUN_ONCE_INIT;
-pub const INIT_ONCE_FN = extern fn (InitOnce: *INIT_ONCE, Parameter: ?*c_void, Context: ?*c_void) BOOL;
+pub const INIT_ONCE_FN = fn (InitOnce: *INIT_ONCE, Parameter: ?*c_void, Context: ?*c_void) callconv(.C) BOOL;
 
 pub const RTL_RUN_ONCE = extern struct {
     Ptr: ?*c_void,
@@ -1418,7 +1418,7 @@ pub const RTL_DRIVE_LETTER_CURDIR = extern struct {
     DosPath: UNICODE_STRING,
 };
 
-pub const PPS_POST_PROCESS_INIT_ROUTINE = ?extern fn () void;
+pub const PPS_POST_PROCESS_INIT_ROUTINE = ?fn () callconv(.C) void;
 
 pub const FILE_BOTH_DIR_INFORMATION = extern struct {
     NextEntryOffset: ULONG,
@@ -1438,7 +1438,7 @@ pub const FILE_BOTH_DIR_INFORMATION = extern struct {
 };
 pub const FILE_BOTH_DIRECTORY_INFORMATION = FILE_BOTH_DIR_INFORMATION;
 
-pub const IO_APC_ROUTINE = extern fn (PVOID, *IO_STATUS_BLOCK, ULONG) void;
+pub const IO_APC_ROUTINE = fn (PVOID, *IO_STATUS_BLOCK, ULONG) callconv(.C) void;
 
 pub const CURDIR = extern struct {
     DosPath: UNICODE_STRING,
diff --git a/lib/std/os/windows/ws2_32.zig b/lib/std/os/windows/ws2_32.zig
index 31547036ae..d467a60d17 100644
--- a/lib/std/os/windows/ws2_32.zig
+++ b/lib/std/os/windows/ws2_32.zig
@@ -106,7 +106,7 @@ pub const WSAOVERLAPPED = extern struct {
     hEvent: ?WSAEVENT,
 };
 
-pub const WSAOVERLAPPED_COMPLETION_ROUTINE = extern fn (dwError: DWORD, cbTransferred: DWORD, lpOverlapped: *WSAOVERLAPPED, dwFlags: DWORD) void;
+pub const WSAOVERLAPPED_COMPLETION_ROUTINE = fn (dwError: DWORD, cbTransferred: DWORD, lpOverlapped: *WSAOVERLAPPED, dwFlags: DWORD) callconv(.C) void;
 
 pub const ADDRESS_FAMILY = u16;
 
diff --git a/lib/std/special/test_runner.zig b/lib/std/special/test_runner.zig
index 6dd208e3b4..7403cca9c2 100644
--- a/lib/std/special/test_runner.zig
+++ b/lib/std/special/test_runner.zig
@@ -34,7 +34,7 @@ pub fn main() anyerror!void {
                     std.heap.page_allocator.free(async_frame_buffer);
                     async_frame_buffer = try std.heap.page_allocator.alignedAlloc(u8, std.Target.stack_align, size);
                 }
-                const casted_fn = @ptrCast(async fn () anyerror!void, test_fn.func);
+                const casted_fn = @ptrCast(fn () callconv(.Async) anyerror!void, test_fn.func);
                 break :blk await @asyncCall(async_frame_buffer, {}, casted_fn);
             },
             .blocking => {
diff --git a/lib/std/start.zig b/lib/std/start.zig
index 631bb2e9f8..604c22101c 100644
--- a/lib/std/start.zig
+++ b/lib/std/start.zig
@@ -224,8 +224,7 @@ inline fn initEventLoopAndCallMain() u8 {
     // and we want fewer call frames in stack traces.
     return @call(.{ .modifier = .always_inline }, callMain, .{});
 }
-
-async fn callMainAsync(loop: *std.event.Loop) u8 {
+fn callMainAsync(loop: *std.event.Loop) callconv(.Async) u8 {
     // This prevents the event loop from terminating at least until main() has returned.
     loop.beginOneEvent();
     defer loop.finishOneEvent();