Commit 89f86e46d278a35a613bbc662cdd3f65ffc76ed7 | zig

author	Matthew Lugg <mlugg@mlugg.co.uk> 2026-04-30 10:08:25+01:00
committer	Matthew Lugg <mlugg@mlugg.co.uk> 2026-05-28 08:54:23+01:00
log	89f86e46d278a35a613bbc662cdd3f65ffc76ed7
tree	dfde60a1161cd65aeb0bf975a62c4a4310133ed0
parent	3f1dead2fc5922b588fbfb108f421ca957d6934a
signature	Commit is signed but in an unrecognized format.

std: don't use dyld functions on non-macOS Darwin

65922a2d4 started using some (deprecated but still available) dyld
functions for stack unwinding and debug information on Darwin targets,
because they are significantly faster than `dladdr` (which is the
"correct" thing to use). However, these functions are unavailable on
Darwin targets other than macOS, for instance on iOS. Therefore, on
those targets, we must fall back to the slow `dladdr` path.

1 files changed, 42 insertions(+), 15 deletions(-)

lib
- std
  - debug
    SelfInfo
    MachO.zig

lib/std/debug/SelfInfo/MachO.zig+42-15

...	...	@@ -93,12 +93,28 @@ pub fn getSymbols(
93	93	pub fn getModuleName(si: *SelfInfo, io: Io, address: usize) Error![]const u8 {
94	94	_ = si;
95	95	_ = io;
96		// This function is marked as deprecated; however, it is significantly more
97		// performant than `dladdr` (since the latter also does a very slow symbol
98		// lookup), so let's use it since it's still available.
99		return std.mem.span(std.c.dyld_image_path_containing_address(
100		@ptrFromInt(address),
101		) orelse return error.MissingDebugInfo);
	96	return getModuleNameInner(address) orelse return error.MissingDebugInfo;
	97	}
	98	fn getModuleNameInner(address: usize) ?[]const u8 {
	99	switch (builtin.target.os.tag) {
	100	.macos => {
	101	// This function is marked as deprecated; however, it is significantly more performant
	102	// than `dladdr` (since the latter also does a very slow symbol lookup), so let's just
	103	// use it for the better performance since it's still available.
	104	return std.mem.span(std.c.dyld_image_path_containing_address(
	105	@ptrFromInt(address),
	106	) orelse return null);
	107	},
	108	else => {
	109	// On other Darwin systems, the function used above is entirely unavailable, so we have
	110	// no choice but to use the slow `dladdr`.
	111	var info: std.c.dl_info = undefined;
	112	if (std.c.dladdr(@ptrFromInt(address), &info) == 0) {
	113	return null;
	114	}
	115	return std.mem.span(info.fname);
	116	},
	117	}
102	118	}
103	119	pub fn getModuleSlide(si: *SelfInfo, io: Io, address: usize) Error!usize {
104	120	const gpa = std.debug.getDebugInfoAllocator();
...	...	@@ -446,12 +462,25 @@ fn unwindFrameInner(si: SelfInfo, io: Io, context: UnwindContext) !usize {
446	462
447	463	/// Acquires the mutex on success.
448	464	fn findModule(si: SelfInfo, gpa: Allocator, io: Io, address: usize) Error!Module {
449		// This function is marked as deprecated; however, it is significantly more
450		// performant than `dladdr` (since the latter also does a very slow symbol
451		// lookup), so let's use it since it's still available.
452		const text_base = std.c._dyld_get_image_header_containing_address(
453		@ptrFromInt(address),
454		) orelse return error.MissingDebugInfo;
	465	const text_base: *anyopaque = switch (builtin.target.os.tag) {
	466	.macos => base: {
	467	// This function is marked as deprecated; however, it is significantly more performant
	468	// than `dladdr` (since the latter also does a very slow symbol lookup), so let's just
	469	// use it for the better performance since it's still available.
	470	break :base std.c._dyld_get_image_header_containing_address(
	471	@ptrFromInt(address),
	472	) orelse return error.MissingDebugInfo;
	473	},
	474	else => base: {
	475	// On other Darwin systems, the function used above is entirely unavailable, so we have
	476	// no choice but to use the slow `dladdr`.
	477	var info: std.c.dl_info = undefined;
	478	if (std.c.dladdr(@ptrFromInt(address), &info) == 0) {
	479	return error.MissingDebugInfo;
	480	}
	481	break :base info.fbase;
	482	},
	483	};
455	484	try si.mutex.lock(io);
456	485	errdefer si.mutex.unlock(io);
457	486	const gop = try si.modules.getOrPutAdapted(gpa, @intFromPtr(text_base), Module.Adapter{});
...	...	@@ -563,9 +592,7 @@ const Module = struct {
563	592
564	593	fn getFile(module: Module, gpa: Allocator, io: Io) Error!MachOFile {
565	594	if (module.file == null) {
566		const path = std.mem.span(
567		std.c.dyld_image_path_containing_address(@ptrFromInt(module.text_base)).?,
568		);
	595	const path = getModuleNameInner(module.text_base).?;
569	596	module.file = MachOFile.load(gpa, io, path, builtin.cpu.arch) catch \|err\| switch (err) {
570	597	error.InvalidMachO, error.InvalidDwarf => error.InvalidDebugInfo,
571	598	error.MissingDebugInfo, error.OutOfMemory, error.UnsupportedDebugInfo, error.ReadFailed => \|e\| e,