[Bug libc/14530] New: __extern_always_inline is not always defined but stdlib.h may use it nevertheless

["ldv at altlinux dot org" <sourceware-bugzilla@sourceware.org>]

http://sourceware.org/bugzilla/show_bug.cgi?id=14530

             Bug #: 14530
           Summary: __extern_always_inline is not always defined but
                    stdlib.h may use it nevertheless
           Product: glibc
           Version: unspecified
            Status: NEW
          Keywords: glibc_2.16
          Severity: normal
          Priority: P2
         Component: libc
        AssignedTo: unassigned@sourceware.org
        ReportedBy: ldv@altlinux.org
                CC: drepper.fsp@gmail.com, polacek@redhat.com
    Classification: Unclassified


Commit glibc-2.15-685-g5ac3ea1 introduced a regression:

$ echo '#include <stdlib.h>' |gcc-4.1 -O2 -D_FORTIFY_SOURCE=2 -S -xc++ -
-o/dev/null
/usr/include/bits/stdlib.h:36: error: expected constructor, destructor, or type
conversion before 'char'
/usr/include/stdlib.h:972: error: expected `}' at end of input

$ echo '#include <stdlib.h>' |gcc-4.1 -O2 -D_FORTIFY_SOURCE=2 -E -xc++ - |grep
-A1 __extern_always_inline |head -2
__extern_always_inline __attribute__ ((__warn_unused_result__)) char *
 realpath (const char *__restrict __name, char *__restrict __resolved) throw ()

That is, g++ < 4.3 in fortify mode no longer compiles stdlib.h.

The bug is somewhat similar to
http://sourceware.org/bugzill/show_bug.cgi?id=13741 but is not exactly the
same.

There is one particular hunk of commit glibc-2.15-685-g5ac3ea1 that made the
difference:
-#if __USE_FORTIFY_LEVEL > 0 && defined __extern_always_inline
+#if __USE_FORTIFY_LEVEL > 0 && defined __fortify_function
Before that change, there were no attempts to include bits/stdlib.h in case of
using old g++ in fortify mode, but there were another chances to hit undefined
__extern_always_inline (the last is the subject of #13741).

A proper definition of __extern_always_inline in sys/cdefs.h would fix both
bugs.

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