`CHECK_LIB', `CHECK_FUNC' and macros

[Ludovic Courtès]

Hi again,

Both `AC_CHECK_LIB' and `AC_CHECK_FUNC' check whether a *symbol* can be
found in the given library (or in one of `$LIBS').  However, on Tru64
UNIX 5.1 (aka. Digital UNIX, OSF1, ...) <pthread.h> does the following:

  #define pthread_create __pthread_create

Therefore, `AC_CHECK_LIB([pthread], [pthread_create])' won't work (link
fails) because symbol `pthread_create' does not exist in `libpthread'
(`__pthread_create' does).

As a work around, I did the following:

  AC_CHECK_HEADER([pthread.h],
                  [have_pthread_h="yes"
                   AC_DEFINE([HAVE_PTHREAD_H], [1],
                             [Define to 1 if <pthread.h> is available.])],
                  [have_pthread_h="no"])
  if test "x$have_pthread_h" = "xyes"; then
     AC_MSG_CHECKING([for pthread_create in -lpthread with pthread.h])
     the_old_libs="$LIBS"
     LIBS="-lpthread $LIBS"
     AC_TRY_LINK([#include <pthread.h>],
                 [pthread_create (0, 0, 0, 0);],
                 [have_lib_pthread="yes"],
                 [have_lib_pthread="no"])
     if test "x$have_lib_pthread" = "xyes"; then
        SYSLIBS="-lpthread $SYSLIBS"
        AC_MSG_RESULT([yes])
     else
        LIBS="$the_old_libs"
        AC_MSG_RESULT([no])
     fi
  fi

The same problem might very well arise with other headers/libraries,
unless some standard defines which symbols are mandatory.  What do
people think about it?

Thanks,
Ludovic.