Fix handling of pcre overflow expressions

Summary: Couple of fixes to the handling of pcre compiled expressions that overflow the default pcre cache:

s_pcre_globals should smart-free m_overflow at the end of the request, and should free() the set of overflow expressions themselves.

Reviewed By: @markw65

Differential Revision: D1503955

hphp/runtime/base/preg.cpp

@@ -58,8 +58,19 @@ pcre_cache_entry::~pcre_cache_entry() {
   pcre_free(re);
 }
 
+void PCREglobals::onSessionExit() {
+  for (auto entry: m_overflow) {
+    delete entry;
+  }
+  smart::vector<const pcre_cache_entry*>().swap(m_overflow);
+}
+
 PCREglobals::~PCREglobals() {
-  m_overflow.clear();
+  onSessionExit();
+}
+
+void pcre_session_exit() {
+  s_pcre_globals->onSessionExit();
 }
 
 void PCREglobals::cleanupOnRequestEnd(const pcre_cache_entry* ent) {

hphp/runtime/base/preg.h

@@ -70,6 +70,7 @@ class PCREglobals {
   PCREglobals() { }
   ~PCREglobals();
   void cleanupOnRequestEnd(const pcre_cache_entry* ent);
+  void onSessionExit();
   // pcre ini_settings
   int64_t m_preg_backtrace_limit;
   int64_t m_preg_recursion_limit;

hphp/runtime/base/program-functions.cpp

@@ -1854,6 +1854,9 @@ void hphp_session_exit() {
     // reinitialize g_context here.
     g_context.getCheck();
 
+    // Clean up pcre state at the end of the request.
+    pcre_session_exit();
+
     mm.sweep();
 
     // Destroy g_context again because ExecutionContext has

hphp/runtime/base/program-functions.h

@@ -83,6 +83,7 @@ class ExecutionContext;
 
 void pcre_init();
 void pcre_reinit();
+void pcre_session_exit();
 void hphp_process_init();
 void hphp_session_init();
 

hphp/test/slow/ext_preg/preg_cache_overflow.php

@@ -0,0 +1,17 @@
+<?php
+
+$matches = 1;
+for ($i=1 ; $i < 1050 ; $i++) {
+  $db_name = 'dbs.'.rand();
+
+  if (preg_match("/^dbs\.(\d+)$/", $db_name, $match)) {
+    $db_num = $match[1];
+    $printable_db_name = preg_replace('/' .$db_num.'/', '%d', $db_name);
+    if (!$printable_db_name) {
+      var_dump("preg_replace returned false");
+      break;
+    }
+    ++$matches;
+  }
+}
+var_dump(sprintf("%d matches", $matches));

hphp/test/slow/ext_preg/preg_cache_overflow.php.expectf

@@ -0,0 +1,5 @@
+string(14) "100000 matches"
+string(14) "100000 matches"
+string(14) "100000 matches"
+string(14) "100000 matches"
+string(14) "100000 matches"

hphp/test/slow/ext_preg/preg_cache_overflow.php.opts

@@ -0,0 +1 @@
+-vEval.PCRETableSize=128 --count 5