strnlen, strict ansi, newlib vs glibc

[Joel Sherrill]

On 9/15/2014 10:12 AM, Thomas Uhle wrote:
> On Sat, 2014-09-13 at 14:57 +0200, Luca Barbato wrote:
>
>> On 14/08/14 17:27, Joel Sherrill wrote:
>>> Hi
>>>
>>> I have some native C++ code that I developed on CentOS and it
>>> has no warnings. Someone moved it to Cygwin and reported warnings
>>> for strnlen() not being prototyped. I investigated and the program did
>>> include string.h. I tried RTEMS tools and got the same as Cygwin
>>> since we have the same string.h from newlib.
>>>
>>> Investigating this, it appears that strnlen() is protected by
>>> __STRICT_ANSI__ on newlib and  __USE_XOPEN2K8 on Linux.
>>>
>>> Command: g++ -Wall -std=c++0x -c strtest.cc
>>>
>>> This program is enough to reproduce the issue:
>>>
>>>     #include <string.h>
>>>
>>>     // size_t strnlen( const char *, size_t );
>>>
>>>     size_t f( const char *str )
>>>     {
>>>       return strnlen( str, 1000 );
>>>     }
>>>
>>>
>>> What do you all think?
>>>
>> Might be nice to add the support for _DEFAULT_SOURCE with the semantic
>> of not filter what is on by default notwithstanding the defines -std
>> might set.
>>
>> It seems supported by glibc and musl so might be good to do as well.
>>
>> lu
>>
> Hello Joel and Luca,
>
> I think that the current guard in newlib/libc/include/string.h:119
>
> #if !defined(__STRICT_ANSI__) || __XSI_VISIBLE >= 500
>
> should be simply replaced by the amended one
>
> #if !defined(__STRICT_ANSI__) || __POSIX_VISIBLE >= 200809 || __XSI_VISIBLE >= 700
>
> to fix this issue.

 If Corinna and/or Jeff is OK with this, then I have no issues as
long as -std=c99 trips the condition based on our cdefs.h. It looks
like it should.

I won't be able to try this for a few days.

Getting these guards just perfect is very tedious and error prone. 

Thanks.

>
> Best regards,
>
> Thomas Uhle
>

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