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Subject: Re: [PATCH] adding missing LTO to some warning options (PR 78606)
To: Martin Sebor <msebor@gmail.com>, Gcc Patch List <gcc-patches@gcc.gnu.org>,	Richard Biener <rguenther@suse.de>
References: <06c24069-90af-5778-52a2-c9167eb109ab@gmail.com>
From: Tom de Vries <Tom_deVries@mentor.com>
Message-ID: <568de1cb-21ed-26ea-8a80-f177f189f293@mentor.com>
Date: Sun, 30 Apr 2017 23:39:00 -0000
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On 01/10/2017 11:16 PM, Martin Sebor wrote:
> +  __builtin_sprintf (d, "%32s", "x");   /* { dg-warning "directive writing 32 bytes into a region of size 12" "-Wformat-length" { xfail *-*-* } } */

This xpasses for me on an older system:
...
XPASS: gcc.dg/pr78768.c -Wformat-overflow (test for warnings, line 11)
...

The mechanism is as follows:
- the system doesn't have linker plugin support, and sets
   HAVE_LTO_PLUGIN to 0
- consequently, opts.c:finish_options() sets x_flag_fat_lto_objects to 1
   in cc1
- cgraphunit.c:symbol_table::compile() does not return
   here:
   ...
      /* Do nothing else if any IPA pass found errors or if we are just
         streaming LTO.  */
      if (seen_error ()
         || (!in_lto_p && flag_lto && !flag_fat_lto_objects))
       {
         timevar_pop (TV_CGRAPHOPT);
         return;
       }
   ...
   and ends up calling expand_all_functions, which calls
   pass_sprintf_length
- the warning is generated by cc1

Maybe the test needs:
...
/* { dg-require-linker-plugin "" } */
...
?

Thanks,
- Tom