change jmp_buf to share an underlying type and struct tag with sigjmp_buf

this is necessary to meet the C++ ABI target. alternatives were
considered to avoid the size increase for non-sig jmp_buf objects, but
they seemed to have worse properties. moreover, the relative size
increase is only extreme on x86[_64]; one way of interpreting this is
that, if the size increase from this patch makes jmp_buf use too much
memory, then the program was already using too much memory when built
for non-x86 archs.

1 files changed, 6 insertions, 7 deletions

diff --git a/include/setjmp.h b/include/setjmp.h
index 5456d8f8..0da27de6 100644
--- a/include/setjmp.h
+++ b/include/setjmp.h
@@ -9,27 +9,26 @@ extern "C" {
 
 #include <bits/setjmp.h>
 
+typedef struct __jmp_buf_tag {
+	__jmp_buf __jb;
+	unsigned long __fl;
+	unsigned long __ss[128/sizeof(long)];
+} jmp_buf[1];
 
 #if defined(_POSIX_SOURCE) || defined(_POSIX_C_SOURCE) \
  || defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) \
  || defined(_BSD_SOURCE)
-typedef struct __sigjmp_buf {
-	jmp_buf __jb;
-	unsigned long __fl;
-	unsigned long __ss[128/sizeof(long)];
-} sigjmp_buf[1];
+typedef jmp_buf sigjmp_buf;
 int sigsetjmp (sigjmp_buf, int);
 _Noreturn void siglongjmp (sigjmp_buf, int);
 #endif
 
-
 #if defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) \
  || defined(_BSD_SOURCE)
 int _setjmp (jmp_buf);
 _Noreturn void _longjmp (jmp_buf, int);
 #endif
 
-
 int setjmp (jmp_buf);
 _Noreturn void longjmp (jmp_buf, int);