Re: [PATCH RFA] configure.in: HAVE_STRUCT_LINK_MAP32 fix

[Michael Snyder <msnyder at redhat dot com>]

Approved, please check it in.

Kevin Buettner wrote:
> 
> The patch below fix the problem in which HAVE_STRUCT_LINK_MAP32 gets
> incorrectly defined for Linux.  The original test is as follows:
> 
>     [AC_TRY_RUN([#define _SYSCALL32
>      #include <sys/link.h>
>      int main()
>      {
>        if (sizeof (struct link_map32) > 0)
>          return 1;
>        return 0;
>      }],
>      gdb_cv_have_struct_link_map32=no,
>      gdb_cv_have_struct_link_map32=yes,
>      gdb_cv_have_struct_link_map32=yes)]
> 
> The problem with this test is that gdb_cv_have_struct_link_map32 is
> defined to be no if the program compiles successfully *and* returns
> 0 when run.  It will be defined to be yes otherwise.  So, on the
> appropriate Solaris system, the test would compile, but the program
> would exit with status code 1 (not 0), thus causing the autoconf
> variable to be defined to yes.
> 
> On Linux, the compilation would simply fail because Linux lacks a
> <sys/link.h> file.  This would also cause the autoconf variable to
> be set to yes.  (Not what we want.)
> 
> I don't think it would ever be possible for the autoconf variable
> to be set to no.  For this to happen, there would have to be a
> struct link_map32 declared which is also of zero size.
> 
> In order for the above test to work, it would have to be written
> as follows:
> 
>     [AC_TRY_RUN([#define _SYSCALL32
>      #include <sys/link.h>
>      int main()
>      {
>        if (sizeof (struct link_map32) > 0)
>          return 0;
>        return 1;
>      }],
>      gdb_cv_have_struct_link_map32=yes,
>      gdb_cv_have_struct_link_map32=no,
>      gdb_cv_have_struct_link_map32=no)]
> 
> Note that the 0 and 1 were interchanged as were the yes/no values.
> 
> However, I don't think AC_TRY_RUN is really appropriate in this case
> anyway because it effectively precludes the use of a cross compiler.
> Instead, I think AC_TRY_COMPILE is sufficient for making the test
> work properly.
> 
> This has been tested on Linux, but not on Solaris.
> 
> Please let me know if it's okay to commit this patch.
> 
>         * configure.in (HAVE_STRUCT_LINK_MAP32): Change test to use
>         AC_TRY_COMPILE instead of AC_TRY_RUN.
> 
> Index: configure.in
> ===================================================================
> RCS file: /cvs/src/src/gdb/configure.in,v
> retrieving revision 1.43
> diff -u -p -r1.43 configure.in
> --- configure.in        2000/08/30 00:58:58     1.43
> +++ configure.in        2000/09/09 20:01:41
> @@ -239,17 +239,10 @@ if test "$ac_cv_header_sys_procfs_h" = y
> 
>    AC_MSG_CHECKING(for struct link_map32 in sys/link.h)
>    AC_CACHE_VAL(gdb_cv_have_struct_link_map32,
> -    [AC_TRY_RUN([#define _SYSCALL32
> -     #include <sys/link.h>
> -     int main()
> -     {
> -       if (sizeof (struct link_map32) > 0)
> -        return 1;
> -       return 0;
> -     }],
> -     gdb_cv_have_struct_link_map32=no,
> +    [AC_TRY_COMPILE([#define _SYSCALL32
> +#include <sys/link.h>], [struct link_map32 l;],
>       gdb_cv_have_struct_link_map32=yes,
> -     gdb_cv_have_struct_link_map32=yes)])
> +     gdb_cv_have_struct_link_map32=no)])
>    AC_MSG_RESULT($gdb_cv_have_struct_link_map32)
>    if test $gdb_cv_have_struct_link_map32 = yes; then
>      AC_DEFINE(HAVE_STRUCT_LINK_MAP32)