[PATCH 2/5] Enable -fsymbolic in LTO if -Bsymbolic is used

[Richard Biener]

On Thu, Oct 22, 2015 at 7:09 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> When -Bsymbolic is passed to linker, references to global symbols
> defined in the shared library are resolved locally.  We should pass
> -fsymbolic to GCC in this case.

Hmm, I think this info should come via the linker plugin, otherwise it
won't work
with using plain 'ld' for linking and plugin auto-loading for example.  Maybe
a special symbol resultion can be used for this?

Richard.

>         * collect2.c (main): Add -fsymbolic to COLLECT_GCC_OPTIONS if
>         -Bsymbolic is used.
>         * doc/invoke.texi: Updated.
> ---
>  gcc/collect2.c      | 51 +++++++++++++++++++++++++++++++++++++++++++++++++--
>  gcc/doc/invoke.texi |  3 ++-
>  2 files changed, 51 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/collect2.c b/gcc/collect2.c
> index 20c2533..ccbf4c3 100644
> --- a/gcc/collect2.c
> +++ b/gcc/collect2.c
> @@ -1044,7 +1044,8 @@ main (int argc, char **argv)
>  #ifndef HAVE_LD_DEMANGLE
>    current_demangling_style = auto_demangling;
>  #endif
> -  p = getenv ("COLLECT_GCC_OPTIONS");
> +  char *gcc_options = getenv ("COLLECT_GCC_OPTIONS");
> +  p = gcc_options;
>    while (p && *p)
>      {
>        const char *q = extract_string (&p);
> @@ -1231,7 +1232,8 @@ main (int argc, char **argv)
>       AIX support needs to know if -shared has been specified before
>       parsing commandline arguments.  */
>
> -  p = getenv ("COLLECT_GCC_OPTIONS");
> +  int add_fsymbolic = -1;
> +  p = gcc_options;
>    while (p && *p)
>      {
>        const char *q = extract_string (&p);
> @@ -1241,6 +1243,9 @@ main (int argc, char **argv)
>         *c_ptr++ = xstrdup (q);
>        if (strcmp (q, "-shared") == 0)
>         shared_obj = 1;
> +      else if (strcmp (q, "-fsymbolic") == 0
> +              || strcmp (q, "-fno-symbolic") == 0)
> +       add_fsymbolic = 0;
>        if (*q == '-' && q[1] == 'B')
>         {
>           *c_ptr++ = xstrdup (q);
> @@ -1278,6 +1283,13 @@ main (int argc, char **argv)
>         {
>           switch (arg[1])
>             {
> +           case 'B':
> +             /* Add -fsymbolic to COLLECT_GCC_OPTIONS if -Bsymbolic is
> +                used.  */
> +             if (add_fsymbolic == -1 && !strcmp (arg + 2, "symbolic"))
> +               add_fsymbolic = 1;
> +             break;
> +
>             case 'd':
>               if (!strcmp (arg, "-debug"))
>                 {
> @@ -1495,6 +1507,41 @@ main (int argc, char **argv)
>         }
>      }
>
> +  if (add_fsymbolic > 0)
> +    {
> +      /* Add -fsymbolic to COLLECT_GCC_OPTIONS.  */
> +      size_t sizeof_env = sizeof "COLLECT_GCC_OPTIONS=";
> +      size_t sizeof_fsymbolic = sizeof "\'-fsymbolic\' ";
> +      size_t len = strlen (gcc_options);
> +      size_t next, start;
> +      char *first;
> +      char *options = (char *) xmalloc (sizeof_env + len +
> +                                       sizeof_fsymbolic - 1);
> +      memcpy (options, "COLLECT_GCC_OPTIONS=", sizeof_env - 1);
> +      first = strchr (gcc_options, '\'');
> +      if (first == NULL)
> +       fatal_error (input_location, "malformed COLLECT_GCC_OPTIONS: %s",
> +                    gcc_options);
> +      next = sizeof_env - 1;
> +      if (first != gcc_options)
> +       {
> +         size_t first_len = first - gcc_options;
> +         memcpy (options + next, gcc_options, first_len);
> +         next += first_len;
> +         start = first_len;
> +       }
> +      else
> +       start = 0;
> +      memcpy (options + next, "\'-fsymbolic\' ", sizeof_fsymbolic - 1);
> +      next += sizeof_fsymbolic - 1;
> +      memcpy (options + next, gcc_options + start, len);
> +      next += len;
> +      options[next] = '\0';
> +      putenv (options);
> +      if (verbose)
> +       fprintf (stderr, "%s\n", options);
> +    }
> +
>  #ifdef COLLECT_EXPORT_LIST
>    /* This is added only for debugging purposes.  */
>    if (debug)
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 5293a25..47baaa3 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -23952,7 +23952,8 @@ which controls how references to global symbols are bound.  The
>  local definitions and external references globally.  This option
>  avoids copy relocations in position-independent executables and
>  optimizes global symbol references in shared library created by
> -linker option, @option{-Bsymbolic}.
> +linker option, @option{-Bsymbolic}.  This option is enabled by default
> +with @option{-flto} when @option{-Bsymbolic} is used.
>
>  @item -fno-ident
>  @opindex fno-ident
> --
> 2.4.3
>