PATCH COMMITTED: PR 6493: Work around -D_FORTIFY_SOURCE

[Ian Lance Taylor]

Michael Hennebry <hennebry@web.cs.ndsu.nodak.edu> writes:

> On Fri, 9 May 2008, Ian Lance Taylor wrote:
>
>> PR 6493 is about a warning in gold when compiling with
>> -D_FORTIFY_SOURCE (at least, I assume they are using that -D option,
>> as otherwise the bug report does not make sense).  In this case gold
>> is calling write in an error case, so it is correctly ignoring the
>> return value.  This patch adds some pointless uses of the return value
>> to avoid the warning.
>
> I thought that was what coercion to void was for.
> It would also have the side-effect of being
> more informative to subsequent readers.

As you can see in the comment I added in the patch, casting to void
did not eliminate the warning when using gcc 4.3.0.  This may be a bug
in gcc 4.3.0; I haven't looked.

Ian

>> Index: gold.cc
>> ===================================================================
>> RCS file: /cvs/src/src/gold/gold.cc,v
>> retrieving revision 1.55
>> diff -p -u -r1.55 gold.cc
>> --- gold.cc     7 May 2008 06:08:01 -0000       1.55
>> +++ gold.cc     9 May 2008 14:12:14 -0000
>> @@ -60,9 +60,18 @@ gold_nomem()
>>    // We are out of memory, so try hard to print a reasonable message.
>>    // Note that we don't try to translate this message, since the
>>    // translation process itself will require memory.
>> -  write(2, program_name, strlen(program_name));
>> -  const char* const s = ": out of memory\n";
>> -  write(2, s, strlen(s));
>> +
>> +  // LEN only exists to avoid a pointless warning when write is
>> +  // declared with warn_use_result, as when compiling with
>> +  // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to
>> +  // work, at least not with gcc 4.3.0.
>> +
>> +  ssize_t len = write(2, program_name, strlen(program_name));
>> +  if (len >= 0)
>> +    {
>> +      const char* const s = ": out of memory\n";
>> +      len = write(2, s, strlen(s));
>
>          (void)write(2, s, strlen(s));
>
>
>> +    }
>>    gold_exit(false);
>>  }
>
> -- 
> Michael   hennebry@web.cs.ndsu.NoDak.edu
> "Those parts of the system that you can hit with a hammer (not advised)
> are called Hardware;  those program instructions that you can only
> curse at are called Software."