Use pcre_free_study() to free PCRE JIT data

Function msc_pcre_cleanup(), which is responsible for freeing
compiled regex data, used either regular free() or pcre_free()
(depending on compilation settings) to free pcre_extra structure
(pointer to which is stored in regex->pe) created by pcre_study().
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 by regular
free(), 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().
Note that code creating msc_regex_t may allocate regex->pe with
malloc() or pcre_malloc() instead of pcre_study(). This case is
checked by testing if PCRE_EXTRA_EXECUTABLE_JIT flag on
regex->pe->flags is set. msc_pregcomp_ex() does not set that flag
itself (and it memsets the whole structure with zeros after
allocation) and pcre_free_study() actually does the same (it tests
for PCRE_EXTRA_EXECUTABLE_JIT flag, and, if that is zero, calls
pcre_free() on passed pointer).

Fixes #610

Author: asterite3

apache2/msc_pcre.c

@@ -21,11 +21,15 @@
 static apr_status_t msc_pcre_cleanup(msc_regex_t *regex) {
     if (regex != NULL) {
         if (regex->pe != NULL) {
+            if (((pcre_extra *)regex->pe)->flags & PCRE_EXTRA_EXECUTABLE_JIT) {
+                pcre_free_study(regex->pe);
+            } else {
 #if defined(VERSION_NGINX)
-            pcre_free(regex->pe);
+                pcre_free(regex->pe);
 #else
-            free(regex->pe);
+                free(regex->pe);
 #endif
+            }
             regex->pe = NULL;
         }
         if (regex->re != NULL) {