[Bug c/68272] New: Unwanted out-of-line instances for C inline functions that are also GCC builtins.

sorganov at gmail dot com gcc-bugzilla@gcc.gnu.org
Tue Nov 10 11:48:00 GMT 2015


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68272

            Bug ID: 68272
           Summary: Unwanted out-of-line instances for C inline functions
                    that are also GCC builtins.
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sorganov at gmail dot com
  Target Milestone: ---

When compiling C code, GCC generates out-of-line copy of any inline function
that also happens to be a GCC builtin, in every compilation unit that gets
inline definition, resulting in link errors (see a test-case below). 

This violates C standard, as according to the standard, an out-of-line copy of
inline function should only be put in those compilation unit(s) where the
function is declared 'extern' as well.

To reproduce (notice no 'extern' declaration ever):

$ cat inl.h
inline int abs(int i) { return (i >= 0) ? i : -i; }
$ cat a.c
#include "inl.h"
int main() { return 1; }
$ cat b.c
#include "inl.h"
$ gcc a.c b.c
/tmp/ccyZFKSx.o: In function `abs':
b.c:(.text+0x0): multiple definition of `abs'
/tmp/ccijz638.o:a.c:(.text+0x0): first defined here
collect2: error: ld returned 1 exit status
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/i586-linux-gnu/4.9/lto-wrapper
Target: i586-linux-gnu
Configured with: [...]
Thread model: posix
gcc version 4.9.2 (Debian 4.9.2-10) 
$


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