don't override Module.print and printErr if the user specified them

2 files changed, 23 insertions, 7 deletions

diff --git a/src/shell.js b/src/shell.js
index b41fbb51..84844c85 100644
--- a/src/shell.js
+++ b/src/shell.js
@@ -38,10 +38,10 @@ var ENVIRONMENT_IS_SHELL = !ENVIRONMENT_IS_WEB && !ENVIRONMENT_IS_NODE && !ENVIR
 if (ENVIRONMENT_IS_NODE) {
   // Expose functionality in the same simple way that the shells work
   // Note that we pollute the global namespace here, otherwise we break in node
-  Module['print'] = function print(x) {
+  if (!Module['print']) Module['print'] = function print(x) {
     process['stdout'].write(x + '\n');
   };
-  Module['printErr'] = function printErr(x) {
+  if (!Module['printErr']) Module['printErr'] = function printErr(x) {
     process['stderr'].write(x + '\n');
   };
 
@@ -71,7 +71,7 @@ if (ENVIRONMENT_IS_NODE) {
   module['exports'] = Module;
 }
 else if (ENVIRONMENT_IS_SHELL) {
-  Module['print'] = print;
+  if (!Module['print']) Module['print'] = print;
   if (typeof printErr != 'undefined') Module['printErr'] = printErr; // not present in v8 or older sm
 
   if (typeof read != 'undefined') {
@@ -107,16 +107,16 @@ else if (ENVIRONMENT_IS_WEB || ENVIRONMENT_IS_WORKER) {
   }
 
   if (typeof console !== 'undefined') {
-    Module['print'] = function print(x) {
+    if (!Module['print']) Module['print'] = function print(x) {
       console.log(x);
     };
-    Module['printErr'] = function printErr(x) {
+    if (!Module['printErr']) Module['printErr'] = function printErr(x) {
       console.log(x);
     };
   } else {
     // Probably a worker, and without console.log. We can do very little here...
     var TRY_USE_DUMP = false;
-    Module['print'] = (TRY_USE_DUMP && (typeof(dump) !== "undefined") ? (function(x) {
+    if (!Module['print']) Module['print'] = (TRY_USE_DUMP && (typeof(dump) !== "undefined") ? (function(x) {
       dump(x);
     }) : (function(x) {
       // self.postMessage(x); // enable this if you want stdout to be sent as messages
diff --git a/tests/test_other.py b/tests/test_other.py
index 5e5dd7a6..b2fc4cf6 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -2221,7 +2221,6 @@ mergeInto(LibraryManager.library, {
     process.communicate()
     assert(os.path.isfile(outdir + 'hello_world.obj'))
 
-
   def test_doublestart_bug(self):
     open('code.cpp', 'w').write(r'''
 #include <stdio.h>
@@ -2253,3 +2252,20 @@ Module["preRun"].push(function () {
 
     assert output.count('This should only appear once.') == 1, '\n'+output
 
+  def test_module_print(self):
+    open('code.cpp', 'w').write(r'''
+#include <stdio.h>
+int main(void) {
+  printf("123456789\n");
+  return 0;
+}
+''')
+
+    open('pre.js', 'w').write(r'''
+var Module = { print: function(x) { throw '<{(' + x + ')}>' } };
+''')
+
+    Popen([PYTHON, EMCC, 'code.cpp', '--pre-js', 'pre.js']).communicate()
+    output = run_js(os.path.join(self.get_dir(), 'a.out.js'), stderr=PIPE, full_output=True, engine=NODE_JS)
+    assert r'<{(123456789)}>' in output, output
+