Export system malloc() and free() as emscripten_builtin_malloc() and emscripten_builtin_free() so that applications can have an easier mechanism to just hook in between to the existing malloc and free, but still keep calling the original dlmalloc and dlfree. Bump version to 1.36.12.

Author: juj

emscripten-version.txt

@@ -1,2 +1 @@
-"1.36.11"
-
+"1.36.12"

system/lib/dlmalloc.c

@@ -6017,6 +6017,15 @@ int mspace_mallopt(int param_number, int value) {
 
 #endif /* MSPACES */
 
+// Export malloc and free as duplicate names emscripten_builtin_malloc and
+// emscripten_builtin_free so that applications can replace malloc and free
+// in their code, and make those replacements refer to the original dlmalloc
+// and dlfree from this file.
+// This allows an easy mechanism for hooking into memory allocation.
+#if defined(__EMSCRIPTEN__)
+extern __typeof(malloc) emscripten_builtin_malloc __attribute__((weak, alias("malloc")));
+extern __typeof(free) emscripten_builtin_free __attribute__((weak, alias("free")));
+#endif
 
 /* -------------------- Alternative MORECORE functions ------------------- */
 

system/lib/libc.symbols

@@ -739,6 +739,8 @@
          W malloc_trim
          W malloc_usable_size
          W mallopt
+         W emscripten_builtin_malloc
+         W emscripten_builtin_free
          T mblen
          T mbrlen
          T mbrtowc

tests/test_core.py

@@ -7184,6 +7184,9 @@ def test_brk(self):
   def test_mallinfo(self):
     self.do_run(open(path_from_root('tests', 'mallinfo.cpp')).read(), 'OK.')
 
+  def test_wrap_malloc(self):
+    self.do_run(open(path_from_root('tests', 'wrap_malloc.cpp')).read(), 'OK.')
+
 # Generate tests for everything
 def make_run(fullname, name=-1, compiler=-1, embetter=0, quantum_size=0,
     typed_arrays=0, emcc_args=None, env=None):

tests/wrap_malloc.cpp

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int totalAllocated = 0;
+int totalFreed = 0;
+
+extern "C"
+{
+
+extern void* emscripten_builtin_malloc(size_t bytes);
+extern void emscripten_builtin_free(void* mem);
+
+void * __attribute__((noinline)) malloc(size_t size)
+{
+	++totalAllocated;
+	void *ptr = emscripten_builtin_malloc(size);
+	printf("Allocated %u bytes, got %p. %d pointers allocated total.\n", size, ptr, totalAllocated);
+	return ptr;
+}
+
+void __attribute__((noinline)) free(void *ptr)
+{
+	++totalFreed;
+	emscripten_builtin_free(ptr);
+	printf("Freed ptr %p, %d pointers freed total.\n", ptr, totalFreed);
+}
+
+}
+
+int main()
+{
+	for(int i = 0; i < 20; ++i)
+	{
+		void *ptr = malloc(1024 * 1024);
+		free(ptr);
+	}
+	printf("OK.\n");
+}