1 files changed, 54 insertions, 21 deletions

diff --git a/std/debug.zig b/std/debug.zig
index d81e62901a..32f96d3e15 100644
--- a/std/debug.zig
+++ b/std/debug.zig
@@ -12,6 +12,7 @@ const coff = std.coff;
 const pdb = std.pdb;
 const ArrayList = std.ArrayList;
 const builtin = @import("builtin");
+const root = @import("root");
 const maxInt = std.math.maxInt;
 const File = std.fs.File;
 const windows = std.os.windows;
@@ -217,6 +218,12 @@ var panicking: u8 = 0; // TODO make this a bool
 pub fn panicExtra(trace: ?*const builtin.StackTrace, first_trace_addr: ?usize, comptime format: []const u8, args: ...) noreturn {
     @setCold(true);
 
+    if (enable_segfault_handler) {
+        // If a segfault happens while panicking, we want it to actually segfault, not trigger
+        // the handler.
+        resetSegfaultHandler();
+    }
+
     if (@atomicRmw(u8, &panicking, builtin.AtomicRmwOp.Xchg, 1, builtin.AtomicOrder.SeqCst) == 1) {
         // Panicked during a panic.
 
@@ -368,7 +375,7 @@ fn printSourceAtAddressWindows(di: *DebugInfo, out_stream: var, relocated_addres
     const obj_basename = fs.path.basename(mod.obj_file_name);
 
     var symbol_i: usize = 0;
-    const symbol_name = while (symbol_i != mod.symbols.len) {
+    const symbol_name = if (!mod.populated) "???" else while (symbol_i != mod.symbols.len) {
         const prefix = @ptrCast(*pdb.RecordPrefix, &mod.symbols[symbol_i]);
         if (prefix.RecordLen < 2)
             return error.InvalidDebugInfo;
@@ -851,8 +858,10 @@ fn openSelfDebugInfoWindows(allocator: *mem.Allocator) !DebugInfo {
     const age = try pdb_stream.stream.readIntLittle(u32);
     var guid: [16]u8 = undefined;
     try pdb_stream.stream.readNoEof(guid[0..]);
+    if (version != 20000404) // VC70, only value observed by LLVM team
+        return error.UnknownPDBVersion;
     if (!mem.eql(u8, di.coff.guid, guid) or di.coff.age != age)
-        return error.InvalidDebugInfo;
+        return error.PDBMismatch;
     // We validated the executable and pdb match.
 
     const string_table_index = str_tab_index: {
@@ -896,13 +905,18 @@ fn openSelfDebugInfoWindows(allocator: *mem.Allocator) !DebugInfo {
         return error.MissingDebugInfo;
     };
 
-    di.pdb.string_table = di.pdb.getStreamById(string_table_index) orelse return error.InvalidDebugInfo;
+    di.pdb.string_table = di.pdb.getStreamById(string_table_index) orelse return error.MissingDebugInfo;
     di.pdb.dbi = di.pdb.getStream(pdb.StreamType.Dbi) orelse return error.MissingDebugInfo;
 
     const dbi = di.pdb.dbi;
 
     // Dbi Header
     const dbi_stream_header = try dbi.stream.readStruct(pdb.DbiStreamHeader);
+    if (dbi_stream_header.VersionHeader != 19990903) // V70, only value observed by LLVM team
+        return error.UnknownPDBVersion;
+    if (dbi_stream_header.Age != age)
+        return error.UnmatchingPDB;
+
     const mod_info_size = dbi_stream_header.ModInfoSize;
     const section_contrib_size = dbi_stream_header.SectionContributionSize;
 
@@ -2312,39 +2326,58 @@ fn getDebugInfoAllocator() *mem.Allocator {
 
 /// Whether or not the current target can print useful debug information when a segfault occurs.
 pub const have_segfault_handling_support = (builtin.arch == builtin.Arch.x86_64 and builtin.os == .linux) or builtin.os == .windows;
+pub const enable_segfault_handler: bool = if (@hasDecl(root, "enable_segfault_handler"))
+    root.enable_segfault_handler
+else
+    runtime_safety and have_segfault_handling_support;
+
+pub fn maybeEnableSegfaultHandler() void {
+    if (enable_segfault_handler) {
+        std.debug.attachSegfaultHandler();
+    }
+}
+
+var windows_segfault_handle: ?windows.HANDLE = null;
 
 /// Attaches a global SIGSEGV handler which calls @panic("segmentation fault");
 pub fn attachSegfaultHandler() void {
     if (!have_segfault_handling_support) {
         @compileError("segfault handler not supported for this target");
     }
-    switch (builtin.os) {
-        .linux => {
-            var act = os.Sigaction{
-                .sigaction = handleSegfaultLinux,
-                .mask = os.empty_sigset,
-                .flags = (os.SA_SIGINFO | os.SA_RESTART | os.SA_RESETHAND),
-            };
-
-            os.sigaction(os.SIGSEGV, &act, null);
-        },
-        .windows => {
-            _ = windows.kernel32.AddVectoredExceptionHandler(0, handleSegfaultWindows);
-        },
-        else => unreachable,
+    if (windows.is_the_target) {
+        windows_segfault_handle = windows.kernel32.AddVectoredExceptionHandler(0, handleSegfaultWindows);
+        return;
     }
+    var act = os.Sigaction{
+        .sigaction = handleSegfaultLinux,
+        .mask = os.empty_sigset,
+        .flags = (os.SA_SIGINFO | os.SA_RESTART | os.SA_RESETHAND),
+    };
+
+    os.sigaction(os.SIGSEGV, &act, null);
 }
 
-extern fn handleSegfaultLinux(sig: i32, info: *const os.siginfo_t, ctx_ptr: *const c_void) noreturn {
-    // Reset to the default handler so that if a segfault happens in this handler it will crash
-    // the process. Also when this handler returns, the original instruction will be repeated
-    // and the resulting segfault will crash the process rather than continually dump stack traces.
+fn resetSegfaultHandler() void {
+    if (windows.is_the_target) {
+        if (windows_segfault_handle) |handle| {
+            assert(windows.kernel32.RemoveVectoredExceptionHandler(handle) != 0);
+            windows_segfault_handle = null;
+        }
+        return;
+    }
     var act = os.Sigaction{
         .sigaction = os.SIG_DFL,
         .mask = os.empty_sigset,
         .flags = 0,
     };
     os.sigaction(os.SIGSEGV, &act, null);
+}
+
+extern fn handleSegfaultLinux(sig: i32, info: *const os.siginfo_t, ctx_ptr: *const c_void) noreturn {
+    // Reset to the default handler so that if a segfault happens in this handler it will crash
+    // the process. Also when this handler returns, the original instruction will be repeated
+    // and the resulting segfault will crash the process rather than continually dump stack traces.
+    resetSegfaultHandler();
 
     const ctx = @ptrCast(*const os.ucontext_t, @alignCast(@alignOf(os.ucontext_t), ctx_ptr));
     const ip = @intCast(usize, ctx.mcontext.gregs[os.REG_RIP]);