diff --git a/src/library_gl.js b/src/library_gl.js
index 7471578..9228964 100644
--- a/src/library_gl.js
+++ b/src/library_gl.js
@@ -1256,28 +1256,28 @@ var LibraryGL = {
 
     setClientAttribute: function(name, size, type, stride, pointer) {
       var attrib = this.clientAttributes[GL.immediate.ATTRIBUTE_BY_NAME[name]];
       attrib.size = size;
       attrib.type = type;
       attrib.stride = stride;
       attrib.pointer = pointer;
-      attrib.name = name + size;
+      attrib.name = Runtime.getStringConcat(name, size);
     },
 
     // Renderers
     addRendererComponent: function(component) {
       if (this.rendererComponents[component]) return;
       this.rendererComponents[component] = 1;
-      this.renderer += component;
+      this.renderer = Runtime.getStringConcat(this.renderer, component);
     },
 
     setRenderer: function(renderer) {
       var name = renderer;
       if (GL.currProgram && renderer[0] != 'U') {
-        name = 'UD' + GL.currProgram + '|' + renderer; // user-defined program renderer
+        name = Runtime.getStringConcat(Runtime.getStringConcat('UD', GL.currProgram), Runtime.getStringConcat('|', renderer)); // user-defined program renderer
       }
       this.renderer = name;
       if (this.renderers[name]) return this.renderers[name];
       this.renderers[name] = this.createRenderer(renderer);
       return this.renderers[name];
     },
 
@@ -1300,15 +1300,18 @@ var LibraryGL = {
           }
           vertexSize += size * 4; // XXX assuming float
         } else if (which == 'N') {
           vertexSize += 4; // 1 char, + alignment
         } else if (which == 'C') {
           vertexSize += 4; // Up to 4 chars, + alignment
         } else {
-          console.log('Warning: Ignoring renderer attribute ' + which);
+#if ASSERTIONS
+          console.log('Warning: Ignoring renderer attribute');
+          console.log(which);
+#endif
           size = parseInt(renderer[i+1]);
           vertexSize += size * 4; // XXX assuming float
         }
       }
       assert(positionSize > 0);
       // TODO: verify vertexSize is equal to the stride in enabled client arrays
       var useCurrProgram = !!GL.currProgram;
@@ -1465,30 +1468,30 @@ var LibraryGL = {
       var renderer = '', bytes = 0;
       for (var i = 0; i < attributes.length; i++) {
         var attribute = attributes[i];
         if (!attribute) break;
         attribute.offset = attribute.pointer - start;
         if (attribute.offset > bytes) { // ensure we start where we should
           assert((attribute.offset - bytes)%4 == 0); // XXX assuming 4-alignment
-          renderer += '?' + ((attribute.offset - bytes)/4);
+          renderer = Runtime.getStringConcat(renderer, Runtime.getStringConcat('?', ((attribute.offset - bytes)/4)));
           bytes += attribute.offset - bytes;
         }
-        renderer += attribute.name;
+        renderer = Runtime.getStringConcat(renderer, attribute.name);
         bytes += attribute.size * GL.immediate.byteSizeByType[attribute.type];
         if (bytes % 4 != 0) bytes += 4 - (bytes % 4); // XXX assuming 4-alignment
 #if ASSERTIONS
         assert(0 <= attribute.offset && attribute.offset < stride); // must all be in the same buffer
 #endif
       }
 
       assert(stride == 0 || bytes <= stride);
 
       if (bytes < stride) { // ensure the size is that of the stride
         assert((stride - bytes)%4 == 0); // assuming float
-        renderer += '?' + ((stride-bytes)/4);
+        renderer = Runtime.getStringConcat(renderer, Runtime.getStringConcat('?', ((stride-bytes)/4)));
         bytes = stride;
       }
 
       bytes *= count;
       if (!GL.currArrayBuffer) {
         GL.immediate.vertexData = {{{ makeHEAPView('F32', 'start', 'start + bytes') }}}; // XXX assuming float
       }
@@ -1671,15 +1674,15 @@ var LibraryGL = {
   },
 
   glVertexPointer__deps: ['$GLEmulation'], // if any pointers are used, glVertexPointer must be, and if it is, then we need emulation
   glVertexPointer: function(size, type, stride, pointer) {
     GL.immediate.setClientAttribute('V', size, type, stride, pointer);
   },
   glTexCoordPointer: function(size, type, stride, pointer) {
-    GL.immediate.setClientAttribute('T' + GL.immediate.clientActiveTexture, size, type, stride, pointer);
+    GL.immediate.setClientAttribute(Runtime.getStringConcat('T', GL.immediate.clientActiveTexture), size, type, stride, pointer);
   },
   glNormalPointer: function(type, stride, pointer) {
     GL.immediate.setClientAttribute('N', 1, type, stride, pointer);
   },
   glColorPointer: function(size, type, stride, pointer) {
     GL.immediate.setClientAttribute('C', size, type, stride, pointer);
   },
diff --git a/src/runtime.js b/src/runtime.js
index 6a251c4..012a66d 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -319,25 +319,34 @@ var Runtime = {
     if (!Runtime.warnOnce.shown) Runtime.warnOnce.shown = {};
     if (!Runtime.warnOnce.shown[text]) {
       Runtime.warnOnce.shown[text] = 1;
       Module.printErr(text);
     }
   },
 
+  // Cache for JS function wrappers for C functions in FUNCTION_TABLE
   funcWrappers: {},
-
   getFuncWrapper: function(func) {
     if (!Runtime.funcWrappers[func]) {
       Runtime.funcWrappers[func] = function() {
         FUNCTION_TABLE[func].apply(null, arguments);
       };
     }
     return Runtime.funcWrappers[func];
   },
 
+  // Cache for small recurring strings generated by concatenating other
+  // strings, use this to avoid needless allocation and collection
+  stringCache: {},
+  getStringConcat: function(a, b) {
+    var cacheItem = Runtime.stringCache[a];
+    if (!cacheItem) cacheItem = Runtime.stringCache[a] = {};
+    return cacheItem[b] || (cacheItem[b] = a + b);
+  },
+
 #if RUNTIME_DEBUG
   debug: true, // Switch to false at runtime to disable logging at the right times
 
   printObjectList: [],
 
   prettyPrint: function(arg) {
     if (typeof arg == 'undefined') return '!UNDEFINED!';