Hello again,
In fact, there already was the skeleton in MHD to provide what I mean. I
attached a patch fil for the function MHD_set_response_options that
allows to override free() for the response buffer.
The change is quite simple in fact...
I didn't add tests to validate this patch because I wouldn't know where
to put them.
But with this change, I don't need to use MHD_RESPMEM_MUST_COPY anymore!
What do you think?
/Nicolas
Le 19-07-21 à 16 h 10, Nicolas Mora a écrit :
> Hello,
>
> Thanks for the feedback. I totally agree with you on the performance
> side. I myself don't use different malloc()/realloc()/free() than the
> libc one.
>
> The only reason I make this request is because of a bug a user of my
> framework had because of my use of MHD_RESPMEM_MUST_FREE by default
> which caused problems if the response is allocated with a malloc()
> function incompatible with the libc one.
>
> The workaround I found was to use MHD_RESPMEM_MUST_COPY instead, then
> free the bdy response after calling MHD_create_response_from_buffer.
> This works fine that some memory resource is wasted (not for long but
> still).
>
> If not for the specific malloc/free function, would it be possible to
> specify the free() function to deallocate the response body when using
> MHD_RESPMEM_MUST_FREE? Like an option you could pass to MHD_Connection *
> inside the MHD_AccessHandlerCallback function?
>
> Le 19-07-21 à 15 h 44, Christian Grothoff a écrit :
>> 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
>>>
>>
>
diff -x Makefile -x .deps -x '*.rc' -ur libmicrohttpd/src/include/microhttpd.h libmicrohttpd-0.9.65/src/include/microhttpd.h
--- libmicrohttpd/src/include/microhttpd.h 2019-07-21 22:03:05.388191487 -0400
+++ libmicrohttpd-0.9.65/src/include/microhttpd.h 2019-07-05 16:21:24.000000000 -0400
@@ -2887,24 +2887,11 @@
/**
* End of the list of options.
*/
- MHD_RO_END = 0,
-
- /**
- * Set a specific free() function
- * to free response buffer instead of libc void free(void * ptr)
- */
- MHD_RO_FREE_FUNCTION = 0
+ MHD_RO_END = 0
};
/**
- * This typedef is defined to be able to pass a function pointer
- * as a va_arg in MHD_set_response_options
- */
-typedef void(*MHD_free_ptr)(void *);
-
-
-/**
* Set special flags and options for a response.
*
* @param response the response to modify
diff -x Makefile -x .deps -x '*.rc' -ur libmicrohttpd/src/microhttpd/response.c libmicrohttpd-0.9.65/src/microhttpd/response.c
--- libmicrohttpd/src/microhttpd/response.c 2019-07-21 21:51:46.837784832 -0400
+++ libmicrohttpd-0.9.65/src/microhttpd/response.c 2019-06-23 15:20:42.000000000 -0400
@@ -400,6 +400,7 @@
return response;
}
+
/**
* Set special flags and options for a response.
*
@@ -424,15 +425,6 @@
{
switch (ro)
{
- case MHD_RO_FREE_FUNCTION:
- va_start (ap, flags);
- if (NULL != (response->crfc = va_arg (ap, MHD_free_ptr))) {
- ret = MHD_YES;
- } else {
- ret = MHD_NO;
- }
- va_end (ap);
- break;
default:
ret = MHD_NO;
break;
