compat: fall back on __va_copy if available

Since an obvious implementation of va_list is to make it a pointer into the stack frame, implementing va_copy as "dst = src" will work on many systems. Platforms that use something different (e.g., a size-1 array of structs, to be assigned with *(dst) = *(src)) will need some other compatibility macro, though. Luckily, as the glibc manual hints, such systems tend to provide the __va_copy macro (introduced in GCC in March, 1997). By using that if it is available, we can cover our bases pretty well. Discovered by building with CC="gcc -std=c89" on an amd64 machine: $ make CC=c89 strbuf.o [...] strbuf.c: In function 'strbuf_vaddf': strbuf.c:211:2: error: incompatible types when assigning to type 'va_list' from type 'struct __va_list_tag *' make: *** [strbuf.o] Error 1 Explained-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Jonathan Nieder committed Mar 8, 2011 at 02:33 UTC 26db0f2e3afc043e184a5e0ce5eb7c53aeb1f644

1 file changed +10 -1

git-compat-util.h

+10 -1

@@ -536,7 +536,16 @@ void git_qsort(void *base, size_t nmemb, size_t size,

536 #endif

537

538 #ifndef va_copy

539 -#define va_copy(dst,src) (dst) = (src)

539 +/*

540 + * Since an obvious implementation of va_list would be to make it a

541 + * pointer into the stack frame, a simple assignment will work on

542 + * many systems. But let's try to be more portable.

543 + */

544 +#ifdef __va_copy

545 +#define va_copy(dst, src) __va_copy(dst, src)

546 +#else

547 +#define va_copy(dst, src) ((dst) = (src))

548 +#endif

549 #endif

550

551 /*