Modify exit() to throw an object and catch it.

* Changed exit from throwing an text string to throwing
  an Error-derived object encapsulating the exit status.
  Then catch it in 'callMain' and return the status.

  Enable this functionality by setting CATCH_EXIT_CODE in settings.js

3 files changed, 31 insertions, 1 deletions

diff --git a/src/library.js b/src/library.js
index 113c955c..1f63e6d0 100644
--- a/src/library.js
+++ b/src/library.js
@@ -1752,9 +1752,25 @@ LibraryManager.library = {
   _exit: function(status) {
     // void _exit(int status);
     // http://pubs.opengroup.org/onlinepubs/000095399/functions/exit.html
+
+#if CATCH_EXIT_CODE
+    function ExitStatus() {
+      this.name = "ExitStatus";
+      this.message = "Program terminated with exit(" + status + ")";
+      this.status = status;
+    };
+    ExitStatus.prototype = new Error();
+    ExitStatus.prototype.constructor = ExitStatus;
+#endif
+
     __shutdownRuntime__();
     ABORT = true;
+
+#if CATCH_EXIT_CODE
+    throw new ExitStatus();
+#else 
     throw 'exit(' + status + ') called, at ' + new Error().stack;
+#endif
   },
   fork__deps: ['__setErrNo', '$ERRNO_CODES'],
   fork: function() {
diff --git a/src/postamble.js b/src/postamble.js
index c8fd44bd..51ffc6ee 100644
--- a/src/postamble.js
+++ b/src/postamble.js
@@ -17,7 +17,14 @@ Module.callMain = function callMain(args) {
   argv.push(0);
   argv = allocate(argv, 'i32', ALLOC_STATIC);
 
+#if CATCH_EXIT_CODE
+  try {
+    return _main(argc, argv, 0);
+  }
+  catch(e) { if (e.name == "ExitStatus") return e.status; throw e; }
+#else
   return _main(argc, argv, 0);
+#endif
 }
 
 {{GLOBAL_VARS}}
@@ -49,7 +56,10 @@ Module['noInitialRun'] = true;
 #endif
 
 if (!Module['noInitialRun']) {
-  run();
+  var ret = run();
+#if CATCH_EXIT_CODE
+  print('Exit Status: ' + ret);
+#endif
 }
 
 // {{POST_RUN_ADDITIONS}}
diff --git a/src/settings.js b/src/settings.js
index bcda4757..66762298 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -77,6 +77,10 @@ var CLOSURE_INLINE_PREVENTION_LINES = 50; // Functions of this number of lines o
                                           // code generated that tells the closure compiler not to
                                           // inline them. This is useful to prevent the generation of
                                           // overly large functions.
+var CATCH_EXIT_CODE = 0; // If set, causes exit() to throw an exception object which is caught
+                         // in a try..catch block and results in the exit status being
+                         // returned from run(). If zero (the default), the program is just
+                         // terminated with an error message.
 
 // Generated code debugging options
 var SAFE_HEAP = 0; // Check each write to the heap against a list of blocked addresses