Fixes dynamic symbol loading bug on Mac OS X.

On OS X, when you call dlopen() on a null library, and then call dlsym(),
the most recently loaded symbols are always used, no matter what flags
we seem to pass to dlopen().  The solution is to explicitly find the name
of the running executable, and open that as a library.

makefile

@@ -82,7 +82,7 @@ endif
 ifeq ($(platform),darwin)
 	build-cflags = $(common-cflags) -fPIC -fvisibility=hidden \
 		-I$(JAVA_HOME)/include/linux -I$(src)
-	lflags = $(common-lflags) -ldl
+	lflags = $(common-lflags) -ldl -framework CoreFoundation
 	strip-all = -S -x
 	binaryToMacho = $(native-build)/binaryToMacho
 endif

src/posix.cpp

@@ -1,3 +1,6 @@
+#ifdef __APPLE__
+#include "CoreFoundation/CoreFoundation.h"
+#endif
 #include "sys/mman.h"
 #include "sys/types.h"
 #include "sys/stat.h"
@@ -116,6 +119,27 @@ allocate(System* s, unsigned size)
   return p;
 }
 
+void
+pathOfExecutable(System* s, const char** retBuf, unsigned* size)
+{
+#ifdef __APPLE__
+  CFBundleRef bundle = CFBundleGetMainBundle();
+  CFURLRef url = CFBundleCopyExecutableURL(bundle);
+  CFStringRef path = CFURLCopyPath(url);
+  CFIndex pathSize = CFStringGetMaximumSizeOfFileSystemRepresentation(path);
+  char* buffer = reinterpret_cast<char*>(allocate(s, pathSize));
+  if (CFStringGetFileSystemRepresentation(path, buffer, pathSize)) {
+    *size = pathSize;
+    *retBuf = buffer;
+  } else {
+    abort();
+  }
+#else
+  *size = 0;
+  *retBuf = NULL;
+#endif
+}
+
 const bool Verbose = false;
 
 const unsigned Waiting = 1 << 0;
@@ -646,6 +670,7 @@ class MySystem: public System {
                       bool mapName)
   {
     void* p;
+    bool alreadyAllocated = false;
     unsigned nameLength = (name ? strlen(name) : 0);
     if (mapName) {
       unsigned size = nameLength + 3 + sizeof(SO_SUFFIX);
@@ -653,6 +678,10 @@ class MySystem: public System {
       snprintf(buffer, size, "lib%s" SO_SUFFIX, name);
       p = dlopen(buffer, RTLD_LAZY);
     } else {
+      if (!name) {
+        pathOfExecutable(this, &name, &nameLength);
+        alreadyAllocated = true;
+      }
       p = dlopen(name, RTLD_LAZY);
     }
  
@@ -665,6 +694,9 @@ class MySystem: public System {
       if (name) {
         n = static_cast<char*>(allocate(this, nameLength + 1));
         memcpy(n, name, nameLength + 1);
+        if (alreadyAllocated) {
+          free(name, nameLength, false);
+        }
       } else {
         n = 0;
       }

src/system.h

@@ -134,6 +134,7 @@ expect(System* s, bool v)
 
 #ifdef NDEBUG
 
+# undef assert
 # define assert(a, b)
 
 #else // not NDEBUG