Newer compilers default to GNU11, a C11 dialect. Some software however
is unprepared for this or has wrong compatibility checks. What happens
is that some software will for compatibility with C89
#define inline
before inclusion of a standard header, which is undefined behaviour in
C99 and above (C99/C11 7.1.2/4), as inline is a keyword.
If any libc headers that are then included via #include_next provide an
__inline macro definition (current musl does this if C++ or C99 and
above is detected) like the following
#define __inline inline
this results in any __inline token to be preprocessed away.
This breaks use of __builtin_va_arg_pack() in our stdio.h at
compile-time as it can only be used in always inlined functions. The
function attributes __always_inline__ and __gnu_inline__ themselves
require an inline specifier on the function to be applied.
If program includes stdlib.h before limits.h without _XOPEN_SOURCE,
_GNU_SOURCE or _BSD_SOURCE explicitly set, then will it always trigger
the trap with musl libc.
This is becase stdlib.h will pull in features.h which will set
_GNU_SOURCE. This means that the fortify stdlib.h will not include
limits.h but it will still trigger the fortified realpath(), but without
PATH_MAX set.
We fix this by including system stdlib.h before testing if limits.h
should be included.
Since PATH_MAX is known at compile time we can also error at compile
time, instead of compiling a broken realpath().
__builtin_va_arg_pack() is not present in clang along with some
other things like __artificial__ etc.
There will be a fallback mechanism for this implemented in the
next release.
/usr/include/fortify/string.h: In function 'void* __fortify_memcpy(void*, const void*, size_t)':
/usr/include/fortify/string.h:13:12: error: invalid conversion from 'void*' to 'char*' [-fpermissive]
/usr/include/fortify/string.h:14:18: error: invalid conversion from 'const void*' to 'const char*' [-fpermissive]
Since we are relying on GCC anyway, assume void * arithmetic is OK.
