Re: btowc(0) configure check hangs clang? [was: Possible configure bug]

[Bruno Haible]

Aleksander Balicki wrote:
> it was checked with clang-2.9 and trunk - the same effect
> 
> it compiles under gcc-4.4.5

For reference, the test program is this one:

================ foo.c ====================
#include <string.h>
#include <stddef.h>
#include <stdio.h>
#include <time.h>
#include <wchar.h>
int main ()
{
  if (btowc ('\0') != 0)
    return 1;
  return 0;
}
===========================================

I guess that clang hangs or produces an endless loop because of
this inline definition in <wchar.h>:

extern wint_t __btowc_alias (int __c) __asm ("btowc");
__extern_inline wint_t
__NTH (btowc (int __c))
{ return (__builtin_constant_p (__c) && __c >= '\0' && __c <= '\x7f'
          ? (wint_t) __c : __btowc_alias (__c)); }

Evidently, clang gives a different semantics to __asm than GCC.
But GCC's semantics of __asm is fixed for 20 years.

Conclusion: Needs to be fixed in clang.

Btw, in clang 1.0 (target: x86_64-pc-linux-gnu) it works fine:

$ clang -O2 -D__USE_EXTERN_INLINES foo.c
$ nm a.out | grep btowc
                 U btowc@@GLIBC_2.2.5
$ ./a.out ; echo $?
0

Bruno
-- 
In memoriam Robert Mensah <http://en.wikipedia.org/wiki/Robert_Mensah>