Add xdlopen/xdlsym/xdlclose support routines

  Greetings,

As suggested in
https://sourceware.org/ml/libc-alpha/2017-09/msg00799.html, this patch
implements xdlopen, xdlsym and xdlclose routines which terminate test
program with appropriate message if the corresponding dlfcn.h routine
returns an error.

The patch also converts stdlib/tst-tls-atexit.c to the new routines
(to make sure they work).

Suggested commit message:

---
Implement xdlopen, xdlsym and xdlclose routines which terminate test
program with appropriate message if the corresponding dlfcn.h routine
returns an error.

Use them in stdlib/tst-tls-atexit.c
---
  

On 09/20/2017 06:34 PM, Paul Pluzhnikov wrote:
> Greetings,
> 
> As suggested in
> https://sourceware.org/ml/libc-alpha/2017-09/msg00799.html, this patch
> implements xdlopen, xdlsym and xdlclose routines which terminate test
> program with appropriate message if the corresponding dlfcn.h routine
> returns an error.
> 
> The patch also converts stdlib/tst-tls-atexit.c to the new routines
> (to make sure they work).
> 
> Suggested commit message:
> 
> ---
> Implement xdlopen, xdlsym and xdlclose routines which terminate test
> program with appropriate message if the corresponding dlfcn.h routine
> returns an error.
> 
> Use them in stdlib/tst-tls-atexit.c
> ---

Looks good to me. Thanks for adding to the support functions! :-)

> -- Paul Pluzhnikov
> 
> 
> glibc-xdlfcn-20170920.txt
> 
> 
> 2017-09-20  Paul Pluzhnikov  <ppluzhnikov@google.com>
> 	    Carlos O'Donell  <carlos@redhat.com>
> 
> 	* support/xdlfcn.h: New file.
> 	* support/xdlfcn.c: New file.
> 	* support/Makefile (libsupport-routines): Add xdlfcn.
> 	* stdlib/tst-tls-atexit.c: Use xdlopen, xdlsym, xdlclose.
> 	
> 
> diff --git a/stdlib/tst-tls-atexit.c b/stdlib/tst-tls-atexit.c
> index 6dbf49d460..165909af98 100644
> --- a/stdlib/tst-tls-atexit.c
> +++ b/stdlib/tst-tls-atexit.c
> @@ -31,7 +31,6 @@
>     second handle.  In the end, the DSO should remain loaded due to the
>     RTLD_NODELETE flag being set in the second dlopen call.  */
>  
> -#include <dlfcn.h>
>  #include <pthread.h>
>  #include <stdio.h>
>  #include <unistd.h>
> @@ -39,6 +38,7 @@
>  #include <errno.h>
>  #include <link.h>
>  #include <stdbool.h>
> +#include <support/xdlfcn.h>
>  
>  #ifndef NO_DELETE
>  # define LOADED_IS_GOOD false
> @@ -73,18 +73,12 @@ is_loaded (void)
>  static void *
>  reg_dtor_and_close (void *h)
>  {
> -  void (*reg_dtor) (void) = (void (*) (void)) dlsym (h, "reg_dtor");
> -
> -  if (reg_dtor == NULL)
> -    {
> -      printf ("Unable to find symbol: %s\n", dlerror ());
> -      return (void *) (uintptr_t) 1;
> -    }
> +  void (*reg_dtor) (void) = (void (*) (void)) xdlsym (h, "reg_dtor");
>  
>    reg_dtor ();
>  
>  #ifndef NO_DELETE
> -  dlclose (h);
> +  xdlclose (h);
>  #endif
>  
>    return NULL;
> @@ -119,32 +113,22 @@ static int
>  do_test (void)
>  {
>    /* Load the DSO.  */
> -  void *h1 = dlopen (DSO_NAME, RTLD_LAZY);
> -  if (h1 == NULL)
> -    {
> -      printf ("h1: Unable to load DSO: %s\n", dlerror ());
> -      return 1;
> -    }
> +  void *h1 = xdlopen (DSO_NAME, RTLD_LAZY);
>  
>  #ifndef NO_DELETE
>    if (spawn_thread (h1) != 0)
>      return 1;
>  #endif
>  
> -  void *h2 = dlopen (DSO_NAME, H2_RTLD_FLAGS);
> -  if (h2 == NULL)
> -    {
> -      printf ("h2: Unable to load DSO: %s\n", dlerror ());
> -      return 1;
> -    }
> +  void *h2 = xdlopen (DSO_NAME, H2_RTLD_FLAGS);
>  
>  #ifdef NO_DELETE
>    if (spawn_thread (h1) != 0)
>      return 1;
>  
> -  dlclose (h1);
> +  xdlclose (h1);
>  #endif
> -  dlclose (h2);
> +  xdlclose (h2);
>  
>    /* Check link maps to ensure that the DSO has unloaded.  In the normal case,
>       the DSO should be unloaded if there are no uses.  However, if one of the
> diff --git a/support/Makefile b/support/Makefile
> index 2ace3fa8cc..4c01434afd 100644
> --- a/support/Makefile
> +++ b/support/Makefile
> @@ -66,6 +66,7 @@ libsupport-routines = \
>    xclose \
>    xconnect \
>    xdup2 \
> +  xdlfcn \
>    xfclose \
>    xfopen \
>    xfork \
> diff --git a/support/xdlfcn.c b/support/xdlfcn.c
> new file mode 100644
> index 0000000000..6e3979983d
> --- /dev/null
> +++ b/support/xdlfcn.c
> @@ -0,0 +1,58 @@
> +/* Support functionality for using dlopen/dlclose/dlsym.
> +   Copyright (C) 2017 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#include <support/check.h>
> +#include <support/xdlfcn.h>
> +
> +void *
> +xdlopen (const char *filename, int flags)
> +{
> +  void *dso = dlopen (filename, flags);
> +
> +  if (dso == NULL)
> +    FAIL_EXIT1 ("error: dlopen: %s\n", dlerror ());
> +
> +  /* Clear any errors.  */
> +  dlerror ();
> +
> +  return dso;
> +}
> +
> +void *
> +xdlsym (void *handle, const char *symbol)
> +{
> +  void *sym = dlsym (handle, symbol);
> +
> +  if (sym == NULL)
> +    FAIL_EXIT1 ("error: dlsym: %s\n", dlerror ());
> +
> +  /* Clear any errors.  */
> +  dlerror ();
> +
> +  return sym;
> +}
> +
> +void
> +xdlclose (void *handle)
> +{
> +  if (dlclose (handle) != 0)
> +    FAIL_EXIT1 ("error: dlclose: %s\n", dlerror ());
> +
> +  /* Clear any errors.  */
> +  dlerror ();
> +}
> diff --git a/support/xdlfcn.h b/support/xdlfcn.h
> new file mode 100644
> index 0000000000..9bdcb38d3e
> --- /dev/null
> +++ b/support/xdlfcn.h
> @@ -0,0 +1,34 @@
> +/* Support functionality for using dlopen/dlclose/dlsym.
> +   Copyright (C) 2017 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef SUPPORT_DLOPEN_H
> +#define SUPPORT_DLOPEN_H
> +
> +#include <dlfcn.h>
> +
> +__BEGIN_DECLS
> +
> +/* Each of these terminates process on failure with relevant error message.  */
> +void *xdlopen (const char *filename, int flags);
> +void *xdlsym (void *handle, const char *symbol);
> +void xdlclose (void *handle);
> +
> +
> +__END_DECLS
> +
> +#endif /* SUPPORT_DLOPEN_H */