1 files changed, 98 insertions, 0 deletions
diff --git a/src/corruptionCheck.js b/src/corruptionCheck.js
new file mode 100644
index 00000000..315f5cf0
--- /dev/null
+++ b/src/corruptionCheck.js
@@ -0,0 +1,98 @@
+
+// See settings.js, CORRUPTION_CHECK
+
+var CorruptionChecker = {
+  BUFFER_FACTOR: Math.round({{{ CORRUPTION_CHECK }}}),
+
+  ptrs: {},
+  checks: 0,
+  checkFrequency: 1,
+
+  init: function() {
+    this.realMalloc = _malloc;
+    _malloc = Module['_malloc'] = this.malloc;
+
+    this.realFree = _free;
+    _free = Module['_free'] = this.free;
+
+    if (typeof _realloc != 'undefined') {
+      this.realRealloc = _realloc;
+      _realloc = Module['_realloc'] = this.realloc;
+    }
+
+    __ATEXIT__.push({ func: function() {
+      Module.printErr('No corruption detected, ran ' + CorruptionChecker.checks + ' checks.');
+    } });
+  },
+  malloc: function(size) {
+    if (size <= 0) size = 1; // malloc(0) sometimes happens - just allocate a larger area, no harm
+    CorruptionChecker.checkAll();
+    size = (size+7)&(~7);
+    var allocation = CorruptionChecker.realMalloc(size*(1+2*CorruptionChecker.BUFFER_FACTOR));
+    var ptr = allocation + size*CorruptionChecker.BUFFER_FACTOR;
+    assert(!CorruptionChecker.ptrs[ptr]);
+    CorruptionChecker.ptrs[ptr] = size;
+    CorruptionChecker.fillBuffer(allocation, size*CorruptionChecker.BUFFER_FACTOR);
+    CorruptionChecker.fillBuffer(allocation + size*(1+CorruptionChecker.BUFFER_FACTOR), size*CorruptionChecker.BUFFER_FACTOR);
+    //Module.printErr('malloc ' + size + ' ==> ' + [ptr, allocation]);
+    return ptr;
+  },
+  free: function(ptr) {
+    if (!ptr) return; // ok to free(NULL), does nothing
+    CorruptionChecker.checkAll();
+    var size = CorruptionChecker.ptrs[ptr];
+    //Module.printErr('free ' + ptr + ' of size ' + size);
+    assert(size);
+    var allocation = ptr - size*CorruptionChecker.BUFFER_FACTOR;
+    //Module.printErr('free ' + ptr + ' of size ' + size + ' and allocation ' + allocation);
+    delete CorruptionChecker.ptrs[ptr];
+    CorruptionChecker.realFree(allocation);
+  },
+  realloc: function(ptr, newSize) {
+    //Module.printErr('realloc ' + ptr + ' to size ' + newSize);
+    if (newSize <= 0) newSize = 1; // like in malloc
+    if (!ptr) return CorruptionChecker.malloc(newSize); // realloc(NULL, size) forwards to malloc according to the spec
+    var size = CorruptionChecker.ptrs[ptr];
+    assert(size);
+    var allocation = ptr - size*CorruptionChecker.BUFFER_FACTOR;
+    var newPtr = CorruptionChecker.malloc(newSize);
+    //Module.printErr('realloc ' + ptr + ' to size ' + newSize + ' is now ' + newPtr);
+    var newAllocation = newPtr + newSize*CorruptionChecker.BUFFER_FACTOR;
+    HEAPU8.set(HEAPU8.subarray(ptr, ptr + Math.min(size, newSize)), newPtr);
+    CorruptionChecker.free(ptr);
+    return newPtr;
+  },
+  canary: function(x) {
+    return (x&127) + 10;
+  },
+  fillBuffer: function(buffer, size) {
+    for (var x = buffer; x < buffer + size; x++) {
+      {{{ makeSetValue('x', 0, 'CorruptionChecker.canary(x)', 'i8') }}};
+    }
+  },
+  checkBuffer: function(buffer, size) {
+    for (var x = buffer; x < buffer + size; x++) {
+      if (({{{ makeGetValue('x', 0, 'i8') }}}&255) != CorruptionChecker.canary(x)) {
+        assert(0, 'Heap corruption detected!' + [x, buffer, size, {{{ makeGetValue('x', 0, 'i8') }}}&255, CorruptionChecker.canary(x)]);
+      }
+    }
+  },
+  checkPtr: function(ptr) {
+    var size = CorruptionChecker.ptrs[ptr];
+    assert(size);
+    var allocation = ptr - size*CorruptionChecker.BUFFER_FACTOR;
+    CorruptionChecker.checkBuffer(allocation, size*CorruptionChecker.BUFFER_FACTOR);
+    CorruptionChecker.checkBuffer(allocation + size*(1+CorruptionChecker.BUFFER_FACTOR), size*CorruptionChecker.BUFFER_FACTOR);
+  },
+  checkAll: function(force) {
+    CorruptionChecker.checks++;
+    if (!force && CorruptionChecker.checks % CorruptionChecker.checkFrequency != 0) return;
+    //Module.printErr('checking for corruption ' + (CorruptionChecker.checks/CorruptionChecker.checkFrequency));
+    for (var ptr in CorruptionChecker.ptrs) {
+      CorruptionChecker.checkPtr(ptr, false);
+    }
+  },
+};
+
+CorruptionChecker.init();
+