Re: [LTP] [PATCH] creat07: Drop basename() function call from read-only variable

[Markos C. <Mar...@im...>]

On 02/23/2012 03:38 PM, Cyril Hrubis wrote:

> Hi!
>> test_app is a read-only variable because it is defined as a preprocessor macro.
>> Using basename() on this variable, it will most certainly lead to a segmentation
>> fault in uClibc code. Moreover, there is no need to use basename() at all since
>> the test_app variable is a single string and it does not contain any leading
>> paths.
>>
>> Quote from uClibc's include/libgen.h header:
>>
>> "Return final component of PATH.
>> 	This is the weird XPG version of this function.  It sometimes will
>> 	modify its argument.  Therefore we normally use the GNU version (in
>> 	<string.h>) and only if this header is included make the XPG
>> 	version available under the real name.
>>
>> 	extern char *__xpg_basename (char *__path) __THROW;
>> 	#define basename        __xpg_basename"
> 
> Well in glibc you get version that is not reentrant but doesn't modify
> the source string when _GNU_SOURCE is defined (which is defined in
> creat07.c), so this may be bug in uClibc compatibility.
> 
> And I think that there is no reason to segfault when the argument
> doesn't need to be modified, which should be the case here. Or did the
> segfault occured in your enviroment?


It segfaults if it modifies the argument because the argument is
read-only. I don't remember when this function modifies the argument but
it certainly is a bit dangerous to use a read-only variable when this
function has known "weird" behaviour

-- 
markos