darwin: update mcontext_t definition for aarch64 to add neon state

lib/std/c/darwin.zig

@@ -151,11 +151,7 @@ pub const ucontext_t = extern struct {
     __mcontext_data: mcontext_t,
 };
 
-pub const mcontext_t = extern struct {
-    es: arch_bits.exception_state,
-    ss: arch_bits.thread_state,
-    fs: arch_bits.float_state,
-};
+pub const mcontext_t = arch_bits.mcontext_t;
 
 extern "c" fn __error() *c_int;
 pub extern "c" fn NSVersionOfRunTimeLibrary(library_name: [*:0]const u8) u32;

lib/std/c/darwin/aarch64.zig

@@ -1,5 +1,12 @@
 // See C headers in
 // lib/libc/include/aarch64-macos.12-gnu/mach/arm/_structs.h
+// lib/libc/include/aarch64-macos.13-none/arm/_mcontext.h
+
+pub const mcontext_t = extern struct {
+    es: exception_state,
+    ss: thread_state,
+    ns: neon_state,
+};
 
 pub const exception_state = extern struct {
     far: u64, // Virtual Fault Address
@@ -17,6 +24,12 @@ pub const thread_state = extern struct {
     __pad: u32,
 };
 
+pub const neon_state = extern struct {
+    q: [32]u128,
+    fpsr: u32,
+    fpcr: u32,
+};
+
 pub const EXC_TYPES_COUNT = 14;
 pub const EXC_MASK_MACHINE = 0;
 

lib/std/c/darwin/x86_64.zig

@@ -1,5 +1,11 @@
 const c = @import("../darwin.zig");
 
+pub const mcontext_t = extern struct {
+    es: exception_state,
+    ss: thread_state,
+    fs: float_state,
+};
+
 pub const exception_state = extern struct {
     trapno: u16,
     cpu: u16,

lib/std/debug.zig

@@ -445,7 +445,14 @@ pub inline fn getContext(context: *StackTraceContext) bool {
     }
 
     const result = have_getcontext and os.system.getcontext(context) == 0;
-    if (native_os == .macos) assert(context.mcsize == @sizeOf(std.c.mcontext_t));
+    if (native_os == .macos) {
+        // TODO: Temp, to discover this size via aarch64 CI
+        if (context.mcsize != @sizeOf(std.c.mcontext_t)) {
+            print("context.mcsize does not match! {} vs {}\n", .{ context.mcsize, @sizeOf(std.c.mcontext_t)});
+        }
+
+        assert(context.mcsize == @sizeOf(std.c.mcontext_t));
+    }
 
     return result;
 }