[PATCH] sigsegv: Fix build on ppc/musl

[Khem Raj]

mcontext is not a standard layout so glibc and musl differ sadly.

Fixes
../../m4-1.4.19/lib/sigsegv.c: In function 'sigsegv_handler':                   
                                                                                
                            ../../m4-1.4.19/lib/sigsegv.c:223:75: error: 
'mcontext_t' has no member named 'uc_regs'; did you mean 'gregs'?               
                                                                 223 | #    
define SIGSEGV_FAULT_STACKPOINTER  ((ucontext_t *) 
ucp)->uc_mcontext.uc_regs->gregs[1]                                             
                                                  |                             
                                              ^~~~~~~

---
 lib/sigsegv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/sigsegv.c b/lib/sigsegv.c
index 696a152..fa0c465 100644
--- a/lib/sigsegv.c
+++ b/lib/sigsegv.c
@@ -217,10 +217,10 @@ int libsigsegv_version = LIBSIGSEGV_VERSION;
 #   define SIGSEGV_FAULT_STACKPOINTER  ((ucontext_t *) 
ucp)->uc_mcontext.gp_regs[1]
 #  else /* 32-bit */
 /* both should be equivalent */
-#   if 0
-#    define SIGSEGV_FAULT_STACKPOINTER  ((ucontext_t *) 
ucp)->uc_mcontext.regs->gpr[1]
+#   if ! defined __GLIBC__
+#      define SIGSEGV_FAULT_STACKPOINTER  ((ucontext_t *) 
ucp)->uc_regs->gregs[1]
 #   else
-#    define SIGSEGV_FAULT_STACKPOINTER  ((ucontext_t *) 
ucp)->uc_mcontext.uc_regs->gregs[1]
+#      define SIGSEGV_FAULT_STACKPOINTER  ((ucontext_t *) 
ucp)->uc_mcontext.uc_regs->gregs[1]
 #   endif
 #  endif
 
-- 
2.35.1