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Re: Potential issue with strstr on x86 with sse4.2 in glibc-2.18

On Tue, 20 Aug 2013, Rich Felker wrote:

> Also, I question whether the set of files that use callbacks is
> complete. Due to fopencookie and register_printf_function, all of
> stdio could potentially call application code. I suspect there are a
> lot more places like this where, due to glibc extensions, functions
> which seemingly do not use callbacks actually might... (malloc?)

As I noted in <>, 
printf should logically be using $(uses-callbacks) but is actually using 

I've expanded the corresponding item on the wiki todo list to request 
better consistency checks.  But I suspect there will be lots of false 
positives - libc functions can call snprintf internally using only 
standard formats, for example, and it would be undefined behavior if a 
user had overridden those standard formats at that time, so the fact that 
a library function calls snprintf does not mean that function can use 
callbacks even though snprintf can - unless it calls snprintf with a fully 
user-controlled format, in which case of course it does need to allow for 
user callbacks.  Likewise, use of qsort with a callback function defined 
within the library is always fine.

Joseph S. Myers

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