Re: [libmicrohttpd] feature request: change malloc/calloc/free functions

[Christian Grothoff]

Hi Nicolas,

Thanks for the proposal, but I don't think this kind of patch belongs
into MHD. malloc() performance is not critical for MHD at all, as MHD
hardly uses malloc(): We mostly use our own custom memory pool, usually
on top of mmap(), to avoid fragmentation issues and to limit memory
consumption per TCP connection.

So I doubt you'd get _any_ performance delta by using Hoard. If I am
wrong and you do have MHD-specific performance measurements that show
that this is not premature optimization, please share them!

Please also consider that there are allocation functions like
strdup()/strndup(), and mixing allocators (malloc going to Hoard,
strdup() to libc) is likely to end in disaster on free(). So in my view
the only _good_ place to add the functions you propose (or Hoard itself)
would be (GNU) libc.

Happy hacking!

Christian

On 7/21/19 9:28 PM, Nicolas Mora wrote:
> I happened to see that MHD doesn't allow to use different
> malloc/calloc/free functions than the one provided by libc.
> 
> This would be useful if the underlying app using MHD uses different
> allocating functions like Hoard: http://www.hoard.org/
> More specifically, when using MHD_RESPMEM_MUST_FREE in a response
> allocated with a different malloc() function, there would be problems.
> 
> I can submit a patch for it.
> Basically, I'd do it by adding functions like this:
> 
> void MHD_set_alloc_funcs(MHD_malloc_t malloc_fn, MHD_calloc_t calloc_fn,
> MHD_free_t free_fn);
> void MHD_get_alloc_funcs(MHD_malloc_t * malloc_fn, MHD_calloc_t *
> calloc_fn, MHD_free_t * free_fn);
> 
> I didn't see any use of realloc() in the source code, so I wouldn't
> allow to change it.
> 
> Then, all internal call to malloc()/calloc()/free() would be replaced by
> MHD_malloc()/MHD_calloc()/MHD_free()
> 
> How about that? Any feedback?
> 
> /Nicolas
>

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