Use right PCRE functions to alloc/free pcre_extra

Allocate pcre_extra structure with pcre_study or pcre_malloc
and free it with pcre_free_study(). Pass flag
PCRE_STUDY_EXTRA_NEEDED to pcre_study telling it to always
allocate pcre_extra because this structure is needed anyway to
configure match limits.
Until this change, pcre_extra was allocated with eigther
pcre_malloc or regular malloc (depending on whether VERSION_NGINX
is defined); function msc_pcre_cleanup(), which is responsible
for freeing compiled regex data, used either regular free() or
pcre_free() (depending VERSION_NGINX too) to free pcre_extra
structure (pointer to which is stored in regex->pe).
Freeing it like this was incorrect, structure returned by
pcre_study() should be freed by function pcre_free_study(). In
case PCRE JIT is used, pcre_study() makes some additional
allocations itself (at least for JITed executable code), which
function pcre_free_study() frees. If pcre_free_study() is not
used a memory leak occurs because, while pcre_extra structure
itself might be freed, some additional data referenced by it is
not. Fix that by calling pcre_free_study() (instead of
free()/pcre_free()) on pointer returned by pcre_study().
There also seems to be no reason to allocate pcre_extra with
regular malloc (and de-allocate it with free()) - there is a
function pcre_malloc(), which is a function pcre_study() itself
would use to allocate that memory, and, in default case,
pcre_malloc and pcre_free will be set to regular malloc and free.
Usage of malloc() seems to be a remaining of old code where
manual allocation of pcre_extra was always done with malloc().
So, remove "#if defined(VERSION_NGINX)" branches and always use
pcre_malloc() for pcre_extra allocation in case pcre_study did not
allocate it yet and always free is with pcre_free_study() (btw.
'pcreapi' man page recommends to replace pcre_free() usages to
deallocate pcre_extra with pcre_free_study()).

Fixes #610

Author: asterite3

apache2/msc_pcre.c

@@ -21,11 +21,7 @@
 static apr_status_t msc_pcre_cleanup(msc_regex_t *regex) {
     if (regex != NULL) {
         if (regex->pe != NULL) {
-#if defined(VERSION_NGINX)
-            pcre_free(regex->pe);
-#else
-            free(regex->pe);
-#endif
+            pcre_free_study(regex->pe);
             regex->pe = NULL;
         }
         if (regex->re != NULL) {
@@ -67,19 +63,15 @@ void *msc_pregcomp_ex(apr_pool_t *pool, const char *pattern, int options,
 
     #ifdef WITH_PCRE_STUDY
         #ifdef WITH_PCRE_JIT
-                pe = pcre_study(regex->re, PCRE_STUDY_JIT_COMPILE, &errptr);
+                pe = pcre_study(regex->re, PCRE_STUDY_EXTRA_NEEDED|PCRE_STUDY_JIT_COMPILE, &errptr);
         #else
-                pe = pcre_study(regex->re, 0, &errptr);
+                pe = pcre_study(regex->re, PCRE_STUDY_EXTRA_NEEDED, &errptr);
         #endif
     #endif
 
     /* Setup the pcre_extra record if pcre_study did not already do it */
     if (pe == NULL) {
-#if defined(VERSION_NGINX)
         pe = pcre_malloc(sizeof(pcre_extra));
-#else
-        pe = malloc(sizeof(pcre_extra));
-#endif
         if (pe == NULL) {
             return NULL;
         }