Hi Evan,
Sorry for the long delay.
> Attached is a proposed patch to fix the compilation issue, designed by
> comparing the 10.4 and 10.5 SDKs. It relies on an implementation detail, but
> I think it's safe to say that the PowerPC headers are frozen at this point.
Looks good. I've verified that, yes, _STRUCT_MCONTEXT is not defined in the
SDK header files from 10.4.
> I have built it on 10.4.
Thanks. Applied in gnulib and in libsigsegv:
2025-04-28 Bruno Haible <br...@clisp.org>
sigsegv: Fix compilation error on Mac OS X 10.4/powerpc.
Patch by Evan Miller <emmil...@gmail.com> in
<https://lists.gnu.org/archive/html/bug-gnulib/2021-08/msg00153.html>.
* lib/sigsegv.c (SIGSEGV_FAULT_STACKPOINTER) [macOS/powerpc: On Mac OS X
<= 10.4, assume struct field names without underscores.
diff --git a/lib/sigsegv.c b/lib/sigsegv.c
index d0519814eb..6d08999075 100644
--- a/lib/sigsegv.c
+++ b/lib/sigsegv.c
@@ -684,7 +684,12 @@ int libsigsegv_version = LIBSIGSEGV_VERSION;
- 'ucontext_t' and 'struct __darwin_ucontext' in <sys/_structs.h>,
- 'struct __darwin_mcontext' in <ppc/_structs.h>, and
- 'struct __darwin_ppc_thread_state' in <mach/ppc/_structs.h>. */
-# define SIGSEGV_FAULT_STACKPOINTER ((ucontext_t *)
ucp)->uc_mcontext->__ss.__r1
+# if !(defined _STRUCT_MCONTEXT || defined _STRUCT_MCONTEXT32 || defined
_STRUCT_MCONTEXT64)
+/* Mac OS X 10.4 and earlier omitted the underscores. */
+# define SIGSEGV_FAULT_STACKPOINTER ((ucontext_t *) ucp)->uc_mcontext->ss.r1
+# else
+# define SIGSEGV_FAULT_STACKPOINTER ((ucontext_t *)
ucp)->uc_mcontext->__ss.__r1
+# endif
# endif
