From 89f86e46d278a35a613bbc662cdd3f65ffc76ed7 Mon Sep 17 00:00:00 2001
From: Matthew Lugg <mlugg@mlugg.co.uk>
Date: Thu, 30 Apr 2026 10:08:25 +0100
Subject: [PATCH] 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.
---
 lib/std/debug/SelfInfo/MachO.zig | 57 +++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 15 deletions(-)

diff --git a/lib/std/debug/SelfInfo/MachO.zig b/lib/std/debug/SelfInfo/MachO.zig
index c35ae03e9b24a5f3bfb4649a56620f15c487cf05..431108cd3f6164769359902f1abccdec720516df 100644
--- a/lib/std/debug/SelfInfo/MachO.zig
+++ b/lib/std/debug/SelfInfo/MachO.zig
@@ -93,12 +93,28 @@ pub fn getSymbols(
 pub fn getModuleName(si: *SelfInfo, io: Io, address: usize) Error![]const u8 {
     _ = si;
     _ = io;
-    // This function is marked as deprecated; however, it is significantly more
-    // performant than `dladdr` (since the latter also does a very slow symbol
-    // lookup), so let's use it since it's still available.
-    return std.mem.span(std.c.dyld_image_path_containing_address(
-        @ptrFromInt(address),
-    ) orelse return error.MissingDebugInfo);
+    return getModuleNameInner(address) orelse return error.MissingDebugInfo;
+}
+fn getModuleNameInner(address: usize) ?[]const u8 {
+    switch (builtin.target.os.tag) {
+        .macos => {
+            // This function is marked as deprecated; however, it is significantly more performant
+            // than `dladdr` (since the latter also does a very slow symbol lookup), so let's just
+            // use it for the better performance since it's still available.
+            return std.mem.span(std.c.dyld_image_path_containing_address(
+                @ptrFromInt(address),
+            ) orelse return null);
+        },
+        else => {
+            // On other Darwin systems, the function used above is entirely unavailable, so we have
+            // no choice but to use the slow `dladdr`.
+            var info: std.c.dl_info = undefined;
+            if (std.c.dladdr(@ptrFromInt(address), &info) == 0) {
+                return null;
+            }
+            return std.mem.span(info.fname);
+        },
+    }
 }
 pub fn getModuleSlide(si: *SelfInfo, io: Io, address: usize) Error!usize {
     const gpa = std.debug.getDebugInfoAllocator();
@@ -446,12 +462,25 @@ fn unwindFrameInner(si: *SelfInfo, io: Io, context: *UnwindContext) !usize {
 
 /// Acquires the mutex on success.
 fn findModule(si: *SelfInfo, gpa: Allocator, io: Io, address: usize) Error!*Module {
-    // This function is marked as deprecated; however, it is significantly more
-    // performant than `dladdr` (since the latter also does a very slow symbol
-    // lookup), so let's use it since it's still available.
-    const text_base = std.c._dyld_get_image_header_containing_address(
-        @ptrFromInt(address),
-    ) orelse return error.MissingDebugInfo;
+    const text_base: *anyopaque = switch (builtin.target.os.tag) {
+        .macos => base: {
+            // This function is marked as deprecated; however, it is significantly more performant
+            // than `dladdr` (since the latter also does a very slow symbol lookup), so let's just
+            // use it for the better performance since it's still available.
+            break :base std.c._dyld_get_image_header_containing_address(
+                @ptrFromInt(address),
+            ) orelse return error.MissingDebugInfo;
+        },
+        else => base: {
+            // On other Darwin systems, the function used above is entirely unavailable, so we have
+            // no choice but to use the slow `dladdr`.
+            var info: std.c.dl_info = undefined;
+            if (std.c.dladdr(@ptrFromInt(address), &info) == 0) {
+                return error.MissingDebugInfo;
+            }
+            break :base info.fbase;
+        },
+    };
     try si.mutex.lock(io);
     errdefer si.mutex.unlock(io);
     const gop = try si.modules.getOrPutAdapted(gpa, @intFromPtr(text_base), Module.Adapter{});
@@ -563,9 +592,7 @@ const Module = struct {
 
     fn getFile(module: *Module, gpa: Allocator, io: Io) Error!*MachOFile {
         if (module.file == null) {
-            const path = std.mem.span(
-                std.c.dyld_image_path_containing_address(@ptrFromInt(module.text_base)).?,
-            );
+            const path = getModuleNameInner(module.text_base).?;
             module.file = MachOFile.load(gpa, io, path, builtin.cpu.arch) catch |err| switch (err) {
                 error.InvalidMachO, error.InvalidDwarf => error.InvalidDebugInfo,
                 error.MissingDebugInfo, error.OutOfMemory, error.UnsupportedDebugInfo, error.ReadFailed => |e| e,
-- 
2.54.0