Regression with source locations in stack traces on Windows

[kcbanner]

Zig Version

0.14.0-dev.40+b8d2323b8

Steps to Reproduce and Observed Behavior

Line numbers in stack traces have regressed recently. I bisected this down to b8d2323.

I can only confirm this on Windows, but this is what I'm seeing:

Incorrect stack trace:

thread 25548 panic: reached unreachable code
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-release\lib\zig\std\debug.zig:412:14: 0x567d3b8d in assert (game.dll.obj)
    if (!ok) unreachable; // assertion failure
             ^
C:\Users\kcbanner\projects\ion\src\asset.zig:1001:15: 0x5680d414 in release (game.dll.obj)
C:\Users\kcbanner\projects\ion\game\src\modes\RenderTestMode.zig:54:36: 0x5683233d in init (game.dll.obj)
    errdefer gs.asset_cache.release(cube_handle);
                                   ^
C:\Users\kcbanner\projects\ion\game\src\game.zig:80:83: 0x568378be in init (game.dll.obj)
    var quat_editor_mode: imgui.QuatEditorMode = .degrees;
                                                                                  ^
C:\Users\kcbanner\projects\ion\game\src\game.zig:599:45: 0x5683e274 in loaded (game.dll.obj)

                                            ^
C:\Users\kcbanner\projects\ion\game\src\game.zig:424:16: 0x567d1256 in init (game.dll.obj)
    gs.?.loaded(game_memory, reloaded) catch |err| {
               ^
C:\Users\kcbanner\projects\ion\src\main.zig:388:44: 0xb77684 in main (ion.exe.obj)
    game_loaded = game_loaded and game.init(&game_memory);
                                           ^
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-release\lib\zig\std\start.zig:497:75: 0xb7b39a in main (ion.exe.obj)
    return callMainWithArgs(@as(usize, @intCast(c_argc)), @as([*][*:0]u8, @ptrCast(c_argv)), envp);
                                                                          ^
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-release\lib\zig\libc\mingw\crt\crtexe.c:267:0: 0xc27f41 in __tmainCRTStartup (crt2.obj)
    mainret = _tmain (argc, argv, envp);

C:\cygwin64\home\kcbanner\kit\zig\build-stage3-release\lib\zig\libc\mingw\crt\crtexe.c:188:0: 0xc27f9b in mainCRTStartup (crt2.obj)
  ret = __tmainCRTStartup ();

???:?:?: 0x7ff932f97343 in ??? (KERNEL32.DLL)
???:?:?: 0x7ff93441cc90 in ??? (ntdll.dll)

Correct stack trace ():

c:\Users\kcbanner\projects\ion>zig-debug build && zig-out\bin\ion.exe
thread 26744 panic: reached unreachable code
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-debug\lib\zig\std\debug.zig:412:14: 0x567d3b8d in assert (game.dll.obj)
    if (!ok) unreachable; // assertion failure
             ^
C:\Users\kcbanner\projects\ion\src\asset.zig:454:15: 0x5680d414 in release (game.dll.obj)
        assert(load_ref_count <= handle_ref_count.*);
              ^
C:\Users\kcbanner\projects\ion\game\src\modes\RenderTestMode.zig:54:36: 0x5683233d in init (game.dll.obj)
    errdefer gs.asset_cache.release(cube_handle);
                                   ^
C:\Users\kcbanner\projects\ion\game\src\game.zig:32:83: 0x568378be in init (game.dll.obj)
                return @unionInit(Mode, field.name, try @field(field.type, "init")(gs));
                                                                                  ^
C:\Users\kcbanner\projects\ion\game\src\game.zig:343:45: 0x5683e274 in loaded (game.dll.obj)
            self.active_mode = try Mode.init(.render_test, self);
                                            ^
C:\Users\kcbanner\projects\ion\game\src\game.zig:424:16: 0x567d1256 in init (game.dll.obj)
    gs.?.loaded(game_memory, reloaded) catch |err| {
               ^
C:\Users\kcbanner\projects\ion\src\main.zig:388:44: 0x8d7684 in main (ion.exe.obj)
    game_loaded = game_loaded and game.init(&game_memory);
                                           ^
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-debug\lib\zig\std\start.zig:497:75: 0x8db39a in main (ion.exe.obj)
    return callMainWithArgs(@as(usize, @intCast(c_argc)), @as([*][*:0]u8, @ptrCast(c_argv)), envp);
                                                                          ^
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-debug\lib\zig\libc\mingw\crt\crtexe.c:267:0: 0x987f41 in __tmainCRTStartup (crt2.obj)
    mainret = _tmain (argc, argv, envp);

C:\cygwin64\home\kcbanner\kit\zig\build-stage3-debug\lib\zig\libc\mingw\crt\crtexe.c:188:0: 0x987f9b in mainCRTStartup (crt2.obj)
  ret = __tmainCRTStartup ();

???:?:?: 0x7ff932f97343 in ??? (KERNEL32.DLL)
???:?:?: 0x7ff93441cc90 in ??? (ntdll.dll

I don't have a simple reduction yet, as this is only occurring in a large project of mine.

The interesting thing is that some of the line numbers are out of range of the actual file contents - for example asset.zig is only 834 lines long, but the stack trace shows 1001.

Bisect log:

git bisect log
git bisect start
# status: waiting for both good and bad commits
# bad: [2b677d1660018434757f9c9efec3c712675e6c47] Sema: fix performance regression
git bisect bad 2b677d1660018434757f9c9efec3c712675e6c47
# status: waiting for good commit(s), bad commit known
# bad: [1ede3af9f6e5923ed1e42cb33e60c0403539c221] std.zig.target: Remove armeb-windows-gnu and aarch64_be-windows-gnu.
git bisect bad 1ede3af9f6e5923ed1e42cb33e60c0403539c221
# status: waiting for good commit(s), bad commit known
# good: [82a934bb912241809ac8029e1fa5843092a7fdf6] Fix futex2_waitv syscall
git bisect good 82a934bb912241809ac8029e1fa5843092a7fdf6
# good: [1fdf13a14825d6e1bd247754e3677cf546ee4020] AstGen: error for redundant `@inComptime()`
git bisect good 1fdf13a14825d6e1bd247754e3677cf546ee4020
# good: [ccd3cc3266762c1fea93cdc0190eaf71718d9e6a] Parse WASM linker flags as base 10, like clang
git bisect good ccd3cc3266762c1fea93cdc0190eaf71718d9e6a
# bad: [5afd774db35e1e12cc49aab5b7f134b741545b80] std: mark Build.args as const
git bisect bad 5afd774db35e1e12cc49aab5b7f134b741545b80
# bad: [edf14777bae56c3a6a155c59f793dc432656c1de] link.Wasm: correctly fetch source location when decl is a type
git bisect bad edf14777bae56c3a6a155c59f793dc432656c1de
# good: [1eaeb4a0a838a783d2060f4e5b3b26b483b26009] Zcu: rework source locations
git bisect good 1eaeb4a0a838a783d2060f4e5b3b26b483b26009
# bad: [f37d0725fa4c6a0b5e4e9ca4d25e2760dc06764d] Sema: fix callconv detection in generic functions
git bisect bad f37d0725fa4c6a0b5e4e9ca4d25e2760dc06764d
# bad: [b8d2323b88e68bb5af061dd7e488f51aa0ae8176] Sema: eliminate Block.src_decl
git bisect bad b8d2323b88e68bb5af061dd7e488f51aa0ae8176
# first bad commit: [b8d2323b88e68bb5af061dd7e488f51aa0ae8176] Sema: eliminate Block.src_decl

Expected Behavior

The line numbers should match the correct version of the stack trace.

[andrewrk]

cc @mlugg - the bisect pointed to b8d2323

[mlugg]

Oh, that's really bizarre...

I have a commit locally which changes src_line in ZIR to be absolute -- I'll see if I can repro this locally, and if so, will see if that commit fixes it. If it does, I'll PR that commit by itself today.

Thanks for the report!

[kcbanner]

A compact reproduction was found by Travis on Discord:

const std = @import("std");

test {
    const alloc = std.testing.allocator;
    var bits = try std.DynamicBitSetUnmanaged.initEmpty(alloc, 20);
    bits.deinit(alloc);
    bits.set(0);
}

For me this produces:

>zig-debug test stack_issue.zig
thread 19224 panic: reached unreachable code
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-debug\lib\zig\std\debug.zig:412:14: 0x3b191d in assert (test.exe.obj)
    if (!ok) unreachable; // assertion failure
             ^
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-debug\lib\zig\std\bit_set.zig:1188:15: 0x3b3ad4 in set (test.exe.obj)
};
              ^
C:\cygwin64\home\kcbanner\temp\stack_issue.zig:7:13: 0x3b1ed5 in test_0 (test.exe.obj)
    bits.set(0);
            ^
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-debug\lib\zig\compiler\test_runner.zig:155:25: 0x3bd52d in mainTerminal (test.exe.obj)
        if (test_fn.func()) |_| {
                        ^
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-debug\lib\zig\compiler\test_runner.zig:35:28: 0x3b3dc8 in main (test.exe.obj)
        return mainTerminal();
                           ^
C:\cygwin64\home\kcbanner\kit\zig\build-stage3-debug\lib\zig\std\start.zig:354:53: 0x3b3b43 in WinStartup (test.exe.obj)
    std.os.windows.ntdll.RtlExitUserProcess(callMain());
                                                    ^
???:?:?: 0x7ff932f97343 in ??? (KERNEL32.DLL)
???:?:?: 0x7ff93441cc90 in ??? (ntdll.dll)

Note that bit_set.zig:1188 should be bit_set.zig:808