msdos_conv.c warning - Re: Current Warnings Report

[Joel Sherrill]

Hi

Replying to myself.  I grabbed the preprocessed source and
used shorter command lines on it. It is -Os vs -O2 on multiple
but not all targets.

[joel at rtbf64a libfs]$ arm-rtems4.11-gcc -Wall -O2  -c unused.c
[joel at rtbf64a libfs]$ arm-rtems4.11-gcc -Wall -Os  -c unused.c
../../../../../../rtems/c/src/../../cpukit/libfs/src/dosfs/msdos_conv.c:
In function 'msdos_filename_utf8_to_long_name_for_save':
../../../../../../rtems/c/src/../../cpukit/libfs/src/dosfs/msdos_conv.c:452:34:
warning: 'c' may be used uninitialized in this function
[-Wmaybe-uninitialized]
         if ( name_size == UTF16_NULL_SIZE && c == UTF16_NULL ) {
                                  ^
Sounds like a bug report in the making.

Sebastian ..I filed a PR, can you add commentary on
why this is a false positive?

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63224
--joel

On 9/11/2014 7:55 AM, Joel Sherrill wrote:
> On 9/11/2014 5:21 AM, Sebastian Huber wrote:
>> The code is awful, but
>>
>> c/src/../../cpukit/libfs/src/dosfs/msdos_conv.c:452:48: warning: 'c' may be 
>> used uninitialized in this function [-Wmaybe-uninitialized]
>>
>> is a false positive.  On which target and GCC version do you get this warning?
>>
> $ grep "cpukit/libfs/src/dosfs/msdos_conv.c:452" log/*
> log/arm-rtl22xx.log:../../../../../../rtems/c/src/../../cpukit/libfs/src/dosfs/msdos_conv.c:452:48:
> warning: 'c' may be used uninitialized in this function [-Wm
>
> Interesting that it is only one BSP.
>
> What is different about the compilation flags for that BSP? And a quick
> check
> pointed out that it uses -mapcs-frame which no other ARM BSP appears to
> use. Could that be it?
>
> And asking here.. why does it use that? What is the impact of removing it?
>
> Sounds like a gcc PR but our fix may be to review the BSP CFLAGS and reduce
> them. It is a very long list and I question them.
>

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
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