throw on writes to absolute memory addresses; fixes #451

2 files changed, 14 insertions, 0 deletions

diff --git a/src/jsifier.js b/src/jsifier.js
index b3c2af1d..1d18f292 100644
--- a/src/jsifier.js
+++ b/src/jsifier.js
@@ -765,6 +765,10 @@ function JSify(data, functionsOnly, givenFunctions) {
     }
     switch (impl) {
       case VAR_NATIVIZED:
+        if (isNumber(item.ident)) {
+          // Direct write to a memory address; this may be an intentional segfault, if not, it is a bug in the source
+          return 'throw "fault on write to ' + item.ident + '";';
+        }
         return item.ident + '=' + value + ';'; // We have the actual value here
         break;
       case VAR_EMULATED:
diff --git a/tests/runner.py b/tests/runner.py
index d6731ed5..1856016f 100755
--- a/tests/runner.py
+++ b/tests/runner.py
@@ -2856,6 +2856,16 @@ def process(filename):
                    extra_emscripten_args=['-H', 'libc/time.h'])
                    #extra_emscripten_args=['-H', 'libc/fcntl.h,libc/sys/unistd.h,poll.h,libc/math.h,libc/langinfo.h,libc/time.h'])
 
+    def test_intentional_fault(self):
+      # Some programs intentionally segfault themselves, we should compile that into a throw
+      src = r'''
+        int main () {
+          *(volatile char *)0 = 0;
+          return 0;
+        }
+        '''
+      self.do_run(src, 'fault on write to 0')
+
     def test_statics(self):
         # static initializers save i16 but load i8 for some reason
         if Settings.SAFE_HEAP: