Sema: check pointer qualifiers before implicit cast

Closes #12881

5 files changed, 19 insertions, 18 deletions

diff --git a/lib/std/json.zig b/lib/std/json.zig
index 548a3db94e..87fe1c9dea 100644
--- a/lib/std/json.zig
+++ b/lib/std/json.zig
@@ -1560,7 +1560,7 @@ fn parseInternal(
                                     }
                                 }
                                 if (field.is_comptime) {
-                                    if (!try parsesTo(field.field_type, @ptrCast(*const field.field_type, field.default_value.?).*, tokens, child_options)) {
+                                    if (!try parsesTo(field.field_type, @ptrCast(*align(1) const field.field_type, field.default_value.?).*, tokens, child_options)) {
                                         return error.UnexpectedValue;
                                     }
                                 } else {
@@ -1587,7 +1587,7 @@ fn parseInternal(
                 if (!fields_seen[i]) {
                     if (field.default_value) |default_ptr| {
                         if (!field.is_comptime) {
-                            const default = @ptrCast(*const field.field_type, default_ptr).*;
+                            const default = @ptrCast(*align(1) const field.field_type, default_ptr).*;
                             @field(r, field.name) = default;
                         }
                     } else {
@@ -1667,7 +1667,7 @@ fn parseInternal(
                             }
 
                             if (ptrInfo.sentinel) |some| {
-                                const sentinel_value = @ptrCast(*const ptrInfo.child, some).*;
+                                const sentinel_value = @ptrCast(*align(1) const ptrInfo.child, some).*;
                                 try arraylist.append(sentinel_value);
                                 const output = arraylist.toOwnedSlice();
                                 return output[0 .. output.len - 1 :sentinel_value];
diff --git a/lib/std/mem.zig b/lib/std/mem.zig
index bf841bff90..4000030fc0 100644
--- a/lib/std/mem.zig
+++ b/lib/std/mem.zig
@@ -297,7 +297,7 @@ pub fn zeroes(comptime T: type) T {
         },
         .Array => |info| {
             if (info.sentinel) |sentinel_ptr| {
-                const sentinel = @ptrCast(*const info.child, sentinel_ptr).*;
+                const sentinel = @ptrCast(*align(1) const info.child, sentinel_ptr).*;
                 return [_:sentinel]info.child{zeroes(info.child)} ** info.len;
             }
             return [_]info.child{zeroes(info.child)} ** info.len;
@@ -443,7 +443,7 @@ pub fn zeroInit(comptime T: type, init: anytype) T {
 
                     inline for (struct_info.fields) |field| {
                         if (field.default_value) |default_value_ptr| {
-                            const default_value = @ptrCast(*const field.field_type, default_value_ptr).*;
+                            const default_value = @ptrCast(*align(1) const field.field_type, default_value_ptr).*;
                             @field(value, field.name) = default_value;
                         }
                     }
@@ -687,7 +687,7 @@ pub fn span(ptr: anytype) Span(@TypeOf(ptr)) {
     const l = len(ptr);
     const ptr_info = @typeInfo(Result).Pointer;
     if (ptr_info.sentinel) |s_ptr| {
-        const s = @ptrCast(*const ptr_info.child, s_ptr).*;
+        const s = @ptrCast(*align(1) const ptr_info.child, s_ptr).*;
         return ptr[0..l :s];
     } else {
         return ptr[0..l];
@@ -719,7 +719,7 @@ fn SliceTo(comptime T: type, comptime end: meta.Elem(T)) type {
                         // to find the value searched for, which is only the case if it matches
                         // the sentinel of the type passed.
                         if (array_info.sentinel) |sentinel_ptr| {
-                            const sentinel = @ptrCast(*const array_info.child, sentinel_ptr).*;
+                            const sentinel = @ptrCast(*align(1) const array_info.child, sentinel_ptr).*;
                             if (end == sentinel) {
                                 new_ptr_info.sentinel = &end;
                             } else {
@@ -734,7 +734,7 @@ fn SliceTo(comptime T: type, comptime end: meta.Elem(T)) type {
                     // to find the value searched for, which is only the case if it matches
                     // the sentinel of the type passed.
                     if (ptr_info.sentinel) |sentinel_ptr| {
-                        const sentinel = @ptrCast(*const ptr_info.child, sentinel_ptr).*;
+                        const sentinel = @ptrCast(*align(1) const ptr_info.child, sentinel_ptr).*;
                         if (end == sentinel) {
                             new_ptr_info.sentinel = &end;
                         } else {
@@ -772,7 +772,7 @@ pub fn sliceTo(ptr: anytype, comptime end: meta.Elem(@TypeOf(ptr))) SliceTo(@Typ
     const length = lenSliceTo(ptr, end);
     const ptr_info = @typeInfo(Result).Pointer;
     if (ptr_info.sentinel) |s_ptr| {
-        const s = @ptrCast(*const ptr_info.child, s_ptr).*;
+        const s = @ptrCast(*align(1) const ptr_info.child, s_ptr).*;
         return ptr[0..length :s];
     } else {
         return ptr[0..length];
@@ -825,7 +825,7 @@ fn lenSliceTo(ptr: anytype, comptime end: meta.Elem(@TypeOf(ptr))) usize {
             .One => switch (@typeInfo(ptr_info.child)) {
                 .Array => |array_info| {
                     if (array_info.sentinel) |sentinel_ptr| {
-                        const sentinel = @ptrCast(*const array_info.child, sentinel_ptr).*;
+                        const sentinel = @ptrCast(*align(1) const array_info.child, sentinel_ptr).*;
                         if (sentinel == end) {
                             return indexOfSentinel(array_info.child, end, ptr);
                         }
@@ -835,7 +835,7 @@ fn lenSliceTo(ptr: anytype, comptime end: meta.Elem(@TypeOf(ptr))) usize {
                 else => {},
             },
             .Many => if (ptr_info.sentinel) |sentinel_ptr| {
-                const sentinel = @ptrCast(*const ptr_info.child, sentinel_ptr).*;
+                const sentinel = @ptrCast(*align(1) const ptr_info.child, sentinel_ptr).*;
                 // We may be looking for something other than the sentinel,
                 // but iterating past the sentinel would be a bug so we need
                 // to check for both.
@@ -849,7 +849,7 @@ fn lenSliceTo(ptr: anytype, comptime end: meta.Elem(@TypeOf(ptr))) usize {
             },
             .Slice => {
                 if (ptr_info.sentinel) |sentinel_ptr| {
-                    const sentinel = @ptrCast(*const ptr_info.child, sentinel_ptr).*;
+                    const sentinel = @ptrCast(*align(1) const ptr_info.child, sentinel_ptr).*;
                     if (sentinel == end) {
                         return indexOfSentinel(ptr_info.child, sentinel, ptr);
                     }
@@ -911,7 +911,7 @@ pub fn len(value: anytype) usize {
             .Many => {
                 const sentinel_ptr = info.sentinel orelse
                     @compileError("length of pointer with no sentinel");
-                const sentinel = @ptrCast(*const info.child, sentinel_ptr).*;
+                const sentinel = @ptrCast(*align(1) const info.child, sentinel_ptr).*;
                 return indexOfSentinel(info.child, sentinel, value);
             },
             .C => {
@@ -2882,7 +2882,8 @@ fn AsBytesReturnType(comptime P: type) type {
 /// Given a pointer to a single item, returns a slice of the underlying bytes, preserving pointer attributes.
 pub fn asBytes(ptr: anytype) AsBytesReturnType(@TypeOf(ptr)) {
     const P = @TypeOf(ptr);
-    return @ptrCast(AsBytesReturnType(P), ptr);
+    const T = AsBytesReturnType(P);
+    return @ptrCast(T, @alignCast(meta.alignment(T), ptr));
 }
 
 test "asBytes" {
diff --git a/lib/std/meta.zig b/lib/std/meta.zig
index 7e64eff49f..993d88eb04 100644
--- a/lib/std/meta.zig
+++ b/lib/std/meta.zig
@@ -204,12 +204,12 @@ pub fn sentinel(comptime T: type) ?Elem(T) {
             switch (info.size) {
                 .Many, .Slice => {
                     const sentinel_ptr = info.sentinel orelse return null;
-                    return @ptrCast(*const info.child, sentinel_ptr).*;
+                    return @ptrCast(*align(1) const info.child, sentinel_ptr).*;
                 },
                 .One => switch (@typeInfo(info.child)) {
                     .Array => |array_info| {
                         const sentinel_ptr = array_info.sentinel orelse return null;
-                        return @ptrCast(*const array_info.child, sentinel_ptr).*;
+                        return @ptrCast(*align(1) const array_info.child, sentinel_ptr).*;
                     },
                     else => {},
                 },
diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index c4dafcd3b8..892cb1e8d3 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -888,7 +888,7 @@ else
 const vdso_clock_gettime_ty = if (builtin.zig_backend == .stage1)
     fn (i32, *timespec) callconv(.C) usize
 else
-    *const fn (i32, *timespec) callconv(.C) usize;
+    *align(1) const fn (i32, *timespec) callconv(.C) usize;
 
 pub fn clock_gettime(clk_id: i32, tp: *timespec) usize {
     if (@hasDecl(VDSO, "CGT_SYM")) {
diff --git a/lib/std/zig/c_translation.zig b/lib/std/zig/c_translation.zig
index 6847a92eae..9fd89ef8fb 100644
--- a/lib/std/zig/c_translation.zig
+++ b/lib/std/zig/c_translation.zig
@@ -193,7 +193,7 @@ pub fn sizeof(target: anytype) usize {
                 const array_info = @typeInfo(ptr.child).Array;
                 if ((array_info.child == u8 or array_info.child == u16) and
                     array_info.sentinel != null and
-                    @ptrCast(*const array_info.child, array_info.sentinel.?).* == 0)
+                    @ptrCast(*align(1) const array_info.child, array_info.sentinel.?).* == 0)
                 {
                     // length of the string plus one for the null terminator.
                     return (array_info.len + 1) * @sizeOf(array_info.child);