The include/libiberty.h file has a check before declaring asprintf: #if defined(HAVE_DECL_ASPRINTF) && !HAVE_DECL_ASPRINTF extern int asprintf (char **, const char *, ...) ATTRIBUTE_PRINTF_2; #endif via a ac_fn_c_check_decl call in libiberty's configure script, HAVE_DECL_ASPRINTF is defined when the following code sample compiles without errors: #include <stdio.h> /* ... tons of includes and constant definitions ... */ int main() { (void) asprintf; return 0; } This compiles if asprintf is defined as a function but fails if it is a macro, which can be tested in this godbolt.org test: https://godbolt.org/z/T5n17c This is the case for asprintf when stdio.h includes bits/stdio2.h and the compiler does not support va_arg_pack(). The former happens via stdio.h when the _FORTIFY_SOURCE level is > 0 and __fortify_function is defined: https://sourceware.org/git/?p=glibc.git;a=blob;f=libio/stdio.h;h=144137cf67aadac3e86844e37f0fe47c45072fd3;hb=HEAD#l866 and the latter causes the definition of asprintf() as a macro:https://sourceware.org/git/?p=glibc.git;a=blob;f=libio/bits/stdio2.h;h=3f0cab1254b02c4348dcd961e38b9805c7cbe834;hb=HEAD#l206 Given this combination, HAVE_DECL_ASPRINTF is 0, which means libiberty will in the end declare its own asprintf, via include/libiberty.h: https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=include/libiberty.h;h=f4c0fe11d6fe3fe0e1cc44c7c6f6266c97c263e4;hb=HEAD#l655 ... which will then fail: ../../libiberty/../include/libiberty.h:627:12: error: expected parameter declarator extern int asprintf (char **, const char *, ...) ATTRIBUTE_PRINTF_2; ^ /usr/include/bits/stdio2.h:207:24: note: expanded from macro 'asprintf' __asprintf_chk (ptr, __USE_FORTIFY_LEVEL - 1, __VA_ARGS__) Clang does not support va_arg_pack(), so this failure occurs when using clang.
I looked into this problem again and I think a potential fix could be as easy as... commit b95eed1938403874be927d4c25b8bbf88ed686ce (HEAD -> master) Author: Timm Bäder <tbaeder@redhat.com> Date: Mon May 10 09:33:26 2021 +0200 libiberty: Check for asprintf/snprintf macros asprintf and snprintf might be defined as a macro, in which case the declarations in libiberty.h should be omitted. This is in particular true for compilers that do not support __va_arg_pack(). diff --git a/include/libiberty.h b/include/libiberty.h index f4c0fe11d6f..51a5bf91219 100644 --- a/include/libiberty.h +++ b/include/libiberty.h @@ -648,7 +648,7 @@ extern void *bsearch_r (const void *, const void *, int (*)(const void *, const void *, void *), void *); -#if defined(HAVE_DECL_ASPRINTF) && !HAVE_DECL_ASPRINTF +#if defined(HAVE_DECL_ASPRINTF) && !HAVE_DECL_ASPRINTF && !defined(asprintf) /* Like sprintf but provides a pointer to malloc'd storage, which must be freed by the caller. */ @@ -672,7 +672,7 @@ extern int vasprintf (char **, const char *, va_list) ATTRIBUTE_PRINTF(2,0); extern char *xvasprintf (const char *, va_list) ATTRIBUTE_MALLOC ATTRIBUTE_PRINTF(1,0); -#if defined(HAVE_DECL_SNPRINTF) && !HAVE_DECL_SNPRINTF +#if defined(HAVE_DECL_SNPRINTF) && !HAVE_DECL_SNPRINTF && !defined(snprintf) /* Like sprintf but prints at most N characters. */ extern int snprintf (char *, size_t, const char *, ...) ATTRIBUTE_PRINTF_3; #endif Does that seem like a sensible thing to do on the GCC side?