Fix mimalloc+asan (#20951)

Mimalloc defined some symbols as strong, but ASan (and other sanitizers I think) need
to override them, so make them weak like dlmalloc and emmalloc do.

Helps #20936

Author: kripken

system/lib/mimalloc/src/alloc-override.c

@@ -35,7 +35,8 @@ typedef struct mi_nothrow_s { int _tag; } mi_nothrow_t;
     #pragma GCC diagnostic ignored "-Wattributes"  // or we get warnings that nodiscard is ignored on a forward
     #define MI_FORWARD(fun)      __attribute__((alias(#fun), used, visibility("default"), copy(fun)));
   #else
-    #define MI_FORWARD(fun)      __attribute__((alias(#fun), used, visibility("default")));
+    // XXX EMSCRIPTEN: Add "weak"
+    #define MI_FORWARD(fun)      __attribute__((alias(#fun), used, visibility("default"), weak));
   #endif
   #define MI_FORWARD1(fun,x)      MI_FORWARD(fun)
   #define MI_FORWARD2(fun,x,y)    MI_FORWARD(fun)
@@ -239,9 +240,11 @@ extern "C" {
   #endif
 
   // No forwarding here due to aliasing/name mangling issues
+  __attribute__((weak)) // XXX EMSCRIPTEN
   void*  valloc(size_t size)               { return mi_valloc(size); }
   void   vfree(void* p)                    { mi_free(p); }
   size_t malloc_good_size(size_t size)     { return mi_malloc_good_size(size); }
+  __attribute__((weak)) // XXX EMSCRIPTEN
   int    posix_memalign(void** p, size_t alignment, size_t size) { return mi_posix_memalign(p, alignment, size); }
 
   // `aligned_alloc` is only available when __USE_ISOC11 is defined.
@@ -252,15 +255,18 @@ extern "C" {
   // Fortunately, in the case where `aligned_alloc` is declared as `static inline` it
   // uses internally `memalign`, `posix_memalign`, or `_aligned_malloc` so we  can avoid overriding it ourselves.
   #if !defined(__GLIBC__) || __USE_ISOC11
+  __attribute__((weak)) // XXX EMSCRIPTEN
   void* aligned_alloc(size_t alignment, size_t size) { return mi_aligned_alloc(alignment, size); }
   #endif
 #endif
 
 // no forwarding here due to aliasing/name mangling issues
 void  cfree(void* p)                                    { mi_free(p); }
 void* pvalloc(size_t size)                              { return mi_pvalloc(size); }
+__attribute__((weak)) // XXX EMSCRIPTEN
 void* reallocarray(void* p, size_t count, size_t size)  { return mi_reallocarray(p, count, size); }
 int   reallocarr(void* p, size_t count, size_t size)    { return mi_reallocarr(p, count, size); }
+__attribute__((weak)) // XXX EMSCRIPTEN
 void* memalign(size_t alignment, size_t size)           { return mi_memalign(alignment, size); }
 void* _aligned_malloc(size_t alignment, size_t size)    { return mi_aligned_alloc(alignment, size); }
 
@@ -270,6 +276,7 @@ void* _aligned_malloc(size_t alignment, size_t size)    { return mi_aligned_allo
   void* __libc_calloc(size_t count, size_t size)        MI_FORWARD2(mi_calloc, count, size)
   void* __libc_realloc(void* p, size_t size)            MI_FORWARD2(mi_realloc, p, size)
   void  __libc_free(void* p)                            MI_FORWARD0(mi_free, p)
+  __attribute__((weak)) // XXX EMSCRIPTEN
   void* __libc_memalign(size_t alignment, size_t size)  { return mi_memalign(alignment, size); }
 
 #ifdef __EMSCRIPTEN__ // emscripten adds some more on top of WASI

test/test_core.py

@@ -9059,6 +9059,10 @@ def test_asan_no_error(self, name):
     'vector': ('test_asan_vector.cpp', [
       'AddressSanitizer: container-overflow on address'
     ]),
+    # some coverage for mimalloc as well
+    'use_after_free_c_mimalloc': ('test_asan_use_after_free.c', [
+      'AddressSanitizer: heap-use-after-free on address',
+    ], ['-sMALLOC=mimalloc']),
   })
   def test_asan(self, name, expected_output, cflags=None):
     if '-Oz' in self.emcc_args: