SAFE_DYNCALLS option

4 files changed, 43 insertions, 1 deletions

diff --git a/src/jsifier.js b/src/jsifier.js
index 5f327076..ff43c8c6 100644
--- a/src/jsifier.js
+++ b/src/jsifier.js
@@ -1401,6 +1401,8 @@ function JSify(data, functionsOnly, givenFunctions) {
       if (ASM_JS) {
         assert(returnType.search(/\("'\[,/) == -1); // XXX need isFunctionType(type, out)
         callIdent = '(' + callIdent + ')&{{{ FTM_' + sig + ' }}}'; // the function table mask is set in emscripten.py
+      } else if (SAFE_DYNCALLS) {
+        callIdent = '(tempInt=' + callIdent + ',tempInt < 0 || tempInt >= FUNCTION_TABLE.length-1 ? abort("dyncall error") : tempInt)';
       }
       callIdent = Functions.getTable(sig) + '[' + callIdent + ']';
     }
diff --git a/src/modules.js b/src/modules.js
index f3c14cd1..7f8a959b 100644
--- a/src/modules.js
+++ b/src/modules.js
@@ -330,9 +330,16 @@ var Functions = {
           }
         }
       }
+      if (SAFE_DYNCALLS) {
+        assert(!ASM_JS, 'cannot emit safe dyncalls in asm');
+        for (var j = 0; j < table.length; j++) {
+          if (table[j] == 0) {
+            table[j] = "function() { abort('dyncall error') }";
+          }
+        }
+      }
       if (table.length > 20) {
         // add some newlines in the table, for readability
-        table = table.slice(0);
         var j = 10;
         while (j+10 < table.length) {
           table[j] += '\n';
diff --git a/src/settings.js b/src/settings.js
index 21b6abcf..308afddc 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -128,6 +128,8 @@ var SAFE_HEAP = 0; // Check each write to the heap, for example, this will give
                    // that 3 is the option you usually want here.
 var SAFE_HEAP_LOG = 0; // Log out all SAFE_HEAP operations
 
+var SAFE_DYNCALLS = 0; // Show stack traces on missing function pointer/virtual method calls
+
 var ASM_HEAP_LOG = 0; // Simple heap logging, like SAFE_HEAP_LOG but cheaper, and in asm.js
 
 var CORRUPTION_CHECK = 0; // When enabled, will emit a buffer area at the beginning and
diff --git a/tests/runner.py b/tests/runner.py
index aae4c460..4c41c72e 100755
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -2806,6 +2806,37 @@ Exiting setjmp function, level: 0, prev_jmp: -1
         ''' % addr
         self.do_run(src, 'segmentation fault' if addr.isdigit() else 'marfoosh')
 
+    def test_safe_dyncalls(self):
+      if Settings.ASM_JS: return self.skip('asm does not support missing function stack traces')
+      if Settings.SAFE_HEAP: return self.skip('safe heap warning will appear instead')
+      if self.emcc_args is None: return self.skip('need libc')
+
+      Settings.SAFE_DYNCALLS = 1
+
+      for cond, body, work in [(True, True, False), (True, False, False), (False, True, True), (False, False, False)]:
+        print cond, body, work
+        src = r'''
+          #include <stdio.h>
+
+          struct Classey {
+            virtual void doIt() = 0;
+          };
+
+          struct D1 : Classey {
+            virtual void doIt() BODY;
+          };
+
+          int main(int argc, char **argv)
+          {
+            Classey *p = argc COND 100 ? new D1() : NULL;
+            printf("%p\n", p);
+            p->doIt();
+
+            return 0;
+          }
+        '''.replace('COND', '==' if cond else '!=').replace('BODY', r'{ printf("all good\n"); }' if body else '')
+        self.do_run(src, 'dyncall error' if not work else 'all good')
+
     def test_dynamic_cast(self):
         if self.emcc_args is None: return self.skip('need libcxxabi')