Cleanup 'zend' command a bit

The [z]end command in hphpd runs the last manually entered snippet of php in "zend". If you typed 'z' before actually entering any php, it would segfault. Fixed a minor bug in Process::Exec, and present help if none entered. Also clarified that it will simply use your system's default php, and made it so you can override which exe to use with a hphpd config variable. The default is "php", since that is most commonly used.

hphp/runtime/debugger/cmd/cmd_zend.cpp

@@ -31,9 +31,10 @@ void CmdZend::help(DebuggerClient &client) {
   client.helpBody(
     "This is mainly for comparing results from PHP vs. HipHop. After you type "
     "in some PHP code, it will be evaluated immediately in HipHop. Then you "
-    "can type '[z]end' command to re-run the same script in Zend PHP. Please "
-    "note that only the most recent block of code you manually typed in was "
-    "evaluated, not any earlier ones, nor the ones from a PHP file."
+    "can type '[z]end' command to re-run the same script with your "
+    "system-default PHP. Please note that only the most recent block of code "
+    "you manually typed in is evaluated, not any earlier ones, nor the ones "
+    "from a PHP file."
   );
 }
 
@@ -42,12 +43,16 @@ void CmdZend::onClientImpl(DebuggerClient &client) {
 
   if (client.argCount() == 0) {
     const std::string &code = client.getCode();
-    string out;
-    Process::Exec("php", nullptr, code.c_str(), out, &out, true);
-    client.print(out);
-  } else {
-    help(client);
+    if (!code.empty()) {
+      const std::string zendExe = client.getZendExecutable();
+      client.info("Executing last PHP block with \"%s\"...", zendExe.c_str());
+      string out;
+      Process::Exec(zendExe.c_str(), nullptr, code.c_str(), out, &out, true);
+      client.print(out);
+      return;
+    }
   }
+  help(client);
 }
 
 ///////////////////////////////////////////////////////////////////////////////

hphp/runtime/debugger/debugger_client.cpp

@@ -2385,6 +2385,7 @@ void DebuggerClient::loadConfig() {
   }
 
   m_sourceRoot = m_config["SourceRoot"].getString();
+  m_zendExe = m_config["ZendExecutable"].getString("php");
 
   if (needToWriteFile) {
     saveConfig(); // so to generate a starter for people

hphp/runtime/debugger/debugger_client.h

@@ -349,6 +349,8 @@ public:
   void usageLogEvent(const std::string &eventName,
                      const std::string &data = "");
 
+  std::string getZendExecutable() const { return m_zendExe; }
+
 private:
   enum InputState {
     TakingCommand,
@@ -494,6 +496,9 @@ private:
 
   // usage logging
   const char *getUsageMode();
+
+  // Zend executable for CmdZend, overridable via config.
+  std::string m_zendExe;
 };
 
 ///////////////////////////////////////////////////////////////////////////////

hphp/util/process.cpp

@@ -157,9 +157,11 @@ bool Process::Exec(const char *path, const char *argv[], const char *in,
     if (WEXITSTATUS(status) != 0) {
       Logger::Verbose("Status %d running command: `%s'\n",
                       WEXITSTATUS(status), path);
-      while (*argv) {
-        Logger::Verbose("  arg: `%s'\n", *argv);
-        argv++;
+      if (argv) {
+        while (*argv) {
+          Logger::Verbose("  arg: `%s'\n", *argv);
+          argv++;
+        }
       }
     } else {
       ret = true;