Here's how I rolled it:
dnl
dnl make sure AIXers have the proper compiler
case "$host_os" in
*aix*)
if test -n "${CC}" ; then
AC_CHECK_PROGS(CC_R, xlc_r cc_r cc)
if test "$CC_R" = cc ; then
AC_MSG_ERROR([pthread support requires cc_r (or other suitable compiler) on AIX])
else
CC=$CC_R
AC_SUBST(CC)
fi
fi
;;
esac
dnl
dnl Check for pthread support
dnl
PTHREAD_CFLAGS=error
PTHREAD_LDFLAGS=error
dnl If it's error, then the user didn't
dnl define it.
if test "x$PTHREAD_LDFLAGS" = xerror; then
AC_CHECK_LIB(pthread, pthread_attr_init, [
PTHREAD_CFLAGS="-D_REENTRANT -D_POSIX_PTHREAD_SEMANTICS"
PTHREAD_LDFLAGS="-lpthread" ])
fi
if test "x$PTHREAD_LDFLAGS" = xerror; then
AC_CHECK_LIB(pthreads, pthread_attr_init, [
PTHREAD_CFLAGS="-D_THREAD_SAFE"
PTHREAD_LDFLAGS="-lpthreads" ])
fi
if test "x$PTHREAD_LDFLAGS" = xerror; then
AC_CHECK_LIB(c_r, pthread_attr_init, [
PTHREAD_CFLAGS="-D_THREAD_SAFE -pthread"
PTHREAD_LDFLAGS="-pthread" ])
fi
if test "x$PTHREAD_LDFLAGS" = xerror; then
AC_CHECK_FUNC(pthread_attr_init, [
PTHREAD_CFLAGS="-D_REENTRANT"
PTHREAD_LDFLAGS="-lpthread" ])
fi
if test $PTHREAD_LDFLAGS = "error"; then
AC_MSG_WARN(pthread library NOT found: guessing and hoping for the
best....)
PTHREAD_CFLAGS="-D_REENTRANT"
PTHREAD_LDFLAGS="-lpthread"
fi
AC_SUBST(PTHREAD_CFLAGS)
AC_SUBST(PTHREAD_LDFLAG)
On Thu, Apr 14, 2005 at 05:03:32PM -0400, Kevin Teich wrote:
> Hello,
>
> I've noticed some strange behavior with the options that configure chooses
> for compiling pthread code. I'm on a Red Hat Linux 7.3 machine using
> autoconf 2.57 and automake 1.6.3.
>
> We use the ACX_PTHREAD macro from ac-archive to configure pthread options,
> from http://www.gnu.org/software/ac-archive/htmldoc/acx_pthread.html .
> configure would execute successfully and determine that -pthread was the
> correct option for this machine, but our programs would not compile, the
> Makefiles generating link errors for undefined pthread symbols.
>
> The reason for this is that when configure does its test to figure out how
> to handle pthreads, it uses a combined compile/link line when testing
> various options. The test it does for -pthread is to set CFLAGS to
> -pthread and leave LIBS blank, and it generates a test like this:
>
> gcc -c -o conftest -pthread test.c
>
> This compiles fine, presumably because gcc breaks this down into two
> separate steps:
>
> gcc -c test.c -pthread
> gcc -o conftest test.o -pthread
>
> So configure sets PTHREAD_CFLAGS to -pthread and PTHREAD_LIBS to nothing.
>
> But, gcc wants -pthread on both its compile line and its link line. I
> don't know enough about gcc to know why, but I've verified it with a tiny
> test program on my own. (For the link line, you can acutally use -pthread
> or -lpthread.)
>
> So when the generated makefile starts building stuff, it does it in the
> normal two steps. So we'd get something like:
>
> gcc -c main.c $PTHREADS_CFLAGS (= -pthread)
> gcc -o main $PTHREADS_LIBS (= empty)
>
> And get a link error. So I added some code to the acinclude.m4 that checks
> to see if configure determined that -pthread was the thing to use, and if
> so, to also add it to PTHREAD_LIBS:
>
> if test x"$PTHREAD_CFLAGS" = x-pthread; then
> PTHREAD_LIBS="-pthread"
> fi
>
> This solved our problem.
>
> Is this a bug, or a logic error in the ACX_PTHREAD macro, or a
> misconfiguration on my part? Did I do the correct thing to fix it, or is
> there another work-around?
>
> Thanks.
>
>
> --
> Kevin Teich
>
>
>
> _______________________________________________
> Autoconf mailing list
> Autoconf@xxxxxxx
> http://lists.gnu.org/mailman/listinfo/autoconf
>
--
#include <stdio.h>
int main(){int a[]={74,117,115,116,32,97,110,111,116,104,101,114,32, \
67,32,104,97,99,107,101,114,10,0}; int *b=a;while(*b>0)putchar(*b++);}
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