I found a root cause and a simpler/better simple fix:

From manpage for gcc on Linux:
       file.s
           Assembler code.

And from Darwin:

       file.s
           Assembler code.  Apple's version of GCC runs the preprocessor on these files as well as
           those ending in .S.

So the problem/difference is that Apple insists on passing the .s through the preprocessor by default when FSF's gcc does not.
The fix appears to be an explict "-xassembler":

$ cat foo.s
.text
# _gsym_test_func
.globl _gsym_test_func
_gsym_test_func:
# _gsym_test_func

$ gcc -std=c99 -c  foo.s
foo.s:2:3: error: invalid preprocessing directive #_gsym_test_func
foo.s:5:3: error: invalid preprocessing directive #_gsym_test_func

$ gcc -std=c99 -c -xassembler foo.s
[no output]

-Paul


On 1/25/2011 2:48 PM, Nathan Hjelm wrote:
Ok, then there are two possible simple fixes:
 - Strip -std from CCASFLAGS if Apple's gcc 4.0 is encountered, or
 - Always strip -std from CCASFLAGS. The flag shouln't have any effect when compiling assembly.

-Nathan
HPC-3, LANL

On Tue, 25 Jan 2011, Paul H. Hargrove wrote:

I can confirm that the problem appears specific to Apple's compiler.

Since the failure was reported to be configure-time, that took less time to check up on that I'd expected.
What I find is that gcc-4.0.0 on Linux/x86 *does* fail the "#_gsym_test_func" test, but for the RIGHT reason, and then goes on to
pass the next test case with the proper form of global symbol.  The relevent portion of config.log appears below.

-Paul

configure:27399: checking prefix for global symbol labels
configure: trying _
configure:27439: gcc -std=gnu99 -O3 -DNDEBUG -finline-functions -fno-strict-aliasing -c conftest.s >conftest.out 2>&1
configure:27442: $? = 0
configure:27447: gcc -std=gnu99 -O3 -DNDEBUG -finline-functions -fno-strict-aliasing -I. conftest_c.c -c > conftest.cmpl 2>&1
configure:27450: $? = 0
configure:27455: gcc -std=gnu99 -O3 -DNDEBUG -finline-functions -fno-strict-aliasing conftest_c.o conftest.o -o conftest    >
conftest.link 2>&1
configure:27458: $? = 1
conftest_c.o: In function `main':
conftest_c.o(.text+0xd): undefined reference to `gsym_test_func'
collect2: ld returned 1 exit status
configure: failed C program was:
#ifdef __cplusplus
extern "C" {
#endif
void gsym_test_func(void);
#ifdef __cplusplus
}
#endif
int
main()
{
    gsym_test_func();
    return 0;
}
configure: failed ASM program was:

.text
# _gsym_test_func
.globl _gsym_test_func
_gsym_test_func:
# _gsym_test_func

configure: trying
configure:27439: gcc -std=gnu99 -O3 -DNDEBUG -finline-functions -fno-strict-aliasing -c conftest.s >conftest.out 2>&1
configure:27442: $? = 0
configure:27447: gcc -std=gnu99 -O3 -DNDEBUG -finline-functions -fno-strict-aliasing -I. conftest_c.c -c > conftest.cmpl 2>&1
configure:27450: $? = 0
configure:27455: gcc -std=gnu99 -O3 -DNDEBUG -finline-functions -fno-strict-aliasing conftest_c.o conftest.o -o conftest    >
conftest.link 2>&1
configure:27458: $? = 0
configure:27496: result:




On 1/25/2011 2:19 PM, Paul H. Hargrove wrote:
      I have gcc-4.0.0 on Linux built from unmodified FSF sources.
      I will try to reproduce.

      -Paul

      On 1/25/2011 1:47 PM, Nathan Hjelm wrote:
            Looks like a bug in Apple's gcc 4.0. I tried the source with gcc 3.4.6 and gcc 4.1.2 on Linux and did not
            see that error.

            I will take a look and see if there is a simple fix to get around this apparent compiler bug.

            -Nathan

            On Tue, 25 Jan 2011, Jeff Squyres wrote:

                  Short version
                  =============

                  MTT turned up a problem with -std=gnu99 on OS X Leopard, which ships with the gcc 4.0
                  compiler (OS X Snow Leopard ships with gcc 4.2, and doesn't have a problem).  Does anyone
                  have gcc 4.0 on Linux?  I'm wondering if the same problem would occur.

                  More details:
                  =============

                        From our friends at Absoft:


                  -----
                  The -std=gnu99 is causing the problem when used with gcc-4.0 ( the default on Leopard with
                  Apple's XCode 3.1 development tools ):

                  BigMac:ompi cag$ gcc --version -std=gnu99 -c conftest.s
                  conftest.s:2:3: error: invalid preprocessing directive #_gsym_test_func
                  conftest.s:5:3: error: invalid preprocessing directive #_gsym_test_func
                  BigMac:ompi cag$ gcc-4.0 -std=gnu99 -c conftest.s
                  conftest.s:2:3: error: invalid preprocessing directive #_gsym_test_func
                  conftest.s:5:3: error: invalid preprocessing directive #_gsym_test_func
                  BigMac:ompi cag$ gcc-4.2 -std=gnu99 -c conftest.s
                  BigMac:ompi cag$

                  On Snow Leopard with Apple's XCode 3.2 development tools, the default compiler is 4.2.
                  -----

                  The compile line he's talking about in particular is from a configure test in
                  opal/config/opal_config_asm.m4, where we're looking for assembly global symbols.  The source
                  that we're trying to compile is:

                  -----
                  .text
                  # _gsym_test_func
                  .globl _gsym_test_func
                  _gsym_test_func:
                  # _gsym_test_func
                  -----

                  (configure tries a few prefixes)

                  But the "#" token with the -std=gnu99 option is causing failures where it shouldn't (i.e., it
                  causes configure to abort because all the assembly tests looking for the global symbols error
                  out due to the # token.

                  So I think we either need to find a workaround for this assembly test or whack the idea of
                  the C99 stuff.  :-(



                  On Jan 24, 2011, at 10:29 AM, Nathan Hjelm wrote:

                        No, they didn't get added (adding them now). I didn't get a chance to add them
                        over the weekend.

                        -Nathan

                        On Mon, 24 Jan 2011, Jeff Squyres wrote:

                              I'm getting these:

                              CC     dummy_component.lo
                              dummy_component.c:25: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c:28: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c:29: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c:30: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c:31: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c:33: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c:34: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c:35: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c:37: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c:39: warning: ISO C90 forbids specifying subobject
                              to initialize
                              dummy_component.c: In function ‘component_open’:
                              dummy_component.c:45: warning: unused variable ‘c’
                              dummy.c:67: warning: ISO C90 forbids specifying subobject to
                              initialize
                              dummy.c:68: warning: ISO C90 forbids specifying subobject to
                              initialize
                              dummy.c:69: warning: ISO C90 forbids specifying subobject to
                              initialize
                              dummy.c:70: warning: ISO C90 forbids specifying subobject to
                              initialize
                              CCLD   mca_debugger_dummy.la

                              Did the autoconf tests not get added?

                              --
                              Jeff Squyres
                              jsquyres@cisco.com
                              For corporate legal information go to:
                              http://www.cisco.com/web/about/doing_business/legal/cri/


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                  --
                  Jeff Squyres
                  jsquyres@cisco.com
                  For corporate legal information go to:
                  http://www.cisco.com/web/about/doing_business/legal/cri/


                  _______________________________________________
                  devel mailing list
                  devel@open-mpi.org
                  http://www.open-mpi.org/mailman/listinfo.cgi/devel

_______________________________________________
devel mailing list
devel@open-mpi.org
http://www.open-mpi.org/mailman/listinfo.cgi/devel


-- 
Paul H. Hargrove                          PHHargrove@lbl.gov
Future Technologies Group
HPC Research Department                   Tel: +1-510-495-2352
Lawrence Berkeley National Laboratory     Fax: +1-510-486-6900


_______________________________________________
devel mailing list
devel@open-mpi.org
http://www.open-mpi.org/mailman/listinfo.cgi/devel


-- 
Paul H. Hargrove                          PHHargrove@lbl.gov
Future Technologies Group
HPC Research Department                   Tel: +1-510-495-2352
Lawrence Berkeley National Laboratory     Fax: +1-510-486-6900


_______________________________________________ devel mailing list devel@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/devel

-- 
Paul H. Hargrove                          PHHargrove@lbl.gov
Future Technologies Group
HPC Research Department                   Tel: +1-510-495-2352
Lawrence Berkeley National Laboratory     Fax: +1-510-486-6900