Re: [PATCH] add support for -Wmismatched-dealloc

[Joseph Myers <joseph@codesourcery.com>]

On Mon, 14 Dec 2020, Martin Sebor via Libc-alpha wrote:

> > I spent some time working around this but in the end it turned out
> > to be too convoluted so I decided to make the attribute a little
> > smarter.  Instead of associating all allocation functions with all
> > deallocation functions (such as fdopen, fopen, fopen64, etc. with
> > fclose, freopen, and freopen64) I changed it so that an allocator
> > only needs to be associated with a single deallocator (a reallocator
> > also needs to be associated with itself).  That makes things quite
> > a bit simpler.
[...]
> The GCC patches have now been committed and the dependency resolved.

I've looked at the attribute documentation now in GCC, but I'm afraid I'm 
unable to understand from that documentation why the proposed glibc patch 
constitutes a valid way of specifying that, for example, it's valid to use 
freopen as a deallocator for FILE pointers opened by functions whose 
attribute only mentions fclose.  Unless there's something I'm missing in 
the documentation or a separate documentation patch that's not yet 
committed, I think more work is needed on the GCC documentation to make 
clear the semantics the glibc patch is asserting for valid combinations of 
allocators and deallocators, so that those semantics can be reviewed for 
correctness.

-- 
Joseph S. Myers
joseph@codesourcery.com