Use the compiler wrapper on Amazon

Makefile

@@ -22,4 +22,5 @@ run: node_modules
 	./node_modules/.bin/supervisor ./app.js
 
 run-amazon: node_modules
-	./node_modules/.bin/supervisor  -- ./app.js --env amazon
+	$(MAKE) -C c-preload
+	./node_modules/.bin/supervisor -- ./app.js --env amazon

app.js

@@ -96,6 +96,11 @@ function compile(req, res) {
         }
         var outputFilename = path.join(dirPath, 'output.S');
         options = options.concat([ '-x', 'c++', '-o', outputFilename, '-S', '-']);
+        var compilerWrapper = props.get("gcc-explorer", "compiler-wrapper");
+        if (compilerWrapper) {
+            options = [compiler].concat(options);
+            compiler = compilerWrapper;
+        }
         var child = child_process.spawn(
             compiler,
             options

c-preload/.gitignore

@@ -0,0 +1 @@
+libpreload.so

c-preload/compiler-wrapper

@@ -1,6 +1,6 @@
 #/bin/sh
 
-export LD_PRELOAD=$(pwd)/libpreload.so
+export LD_PRELOAD=$(dirname $0)/libpreload.so
 export ALLOWED_FOR_CREATE=/tmp 
 export ALLOWED_FOR_READ=/usr/local/include:/usr/include:/usr/lib
 

c-preload/preload.c

@@ -37,7 +37,7 @@ static int allowed_env(const char* pathname, const char* envvar) {
         while (*okpath == ':') ++okpath;
     }
 
-    fprintf(stderr, "Denying access to \"%s\"\n", pathname);
+    fprintf(stderr, "Access to \"%s\" denied by gcc-explorer policy\n", pathname);
     errno = EACCES;
     return 0;
 }

etc/config/gcc-explorer.amazon.properties

@@ -1,3 +1,4 @@
 # Settings overridden for Amazon EC2 instances that power http://gcc.godbolt.org/
 compileTimeoutMs=200
 compilers=/usr/bin/g++-4.4:/usr/bin/g++-4.5:/usr/bin/g++-4.6:/usr/bin/g++-4.7:/usr/bin/arm-linux-gnueabi-g++-4.5:/usr/bin/clang++
+compiler-wrapper=./c-preload/compiler-wrapper