follow-up reallocarr(ay) BSD implementations,

here OpenBSD malloc_conceal api. not much different of classic
malloc/calloc but content not to be dumped in core files.

Author: devnexen

include/mimalloc-override.h

@@ -49,6 +49,9 @@ not accidentally mix pointers from different allocators).
 #define pvalloc(n)              mi_pvalloc(n)
 #define reallocarray(p,s,n)     mi_reallocarray(p,s,n)
 #define reallocarr(p,s,n)       mi_reallocarr(p,s,n)
+#define malloc_conceal(n)       mi_malloc_conceal(n)
+#define calloc_conceal(n,c)     mi_calloc_conceal(n,c)
+#define freezero(p,n)           mi_freezero(p,n)
 #define memalign(a,n)           mi_memalign(a,n)
 #define aligned_alloc(a,n)      mi_aligned_alloc(a,n)
 #define posix_memalign(p,a,n)   mi_posix_memalign(p,a,n)

include/mimalloc.h

@@ -358,6 +358,9 @@ mi_decl_nodiscard mi_decl_export mi_decl_restrict void* mi_aligned_alloc(size_t
 
 mi_decl_nodiscard mi_decl_export void* mi_reallocarray(void* p, size_t count, size_t size) mi_attr_noexcept mi_attr_alloc_size2(2,3);
 mi_decl_nodiscard mi_decl_export int   mi_reallocarr(void* p, size_t count, size_t size) mi_attr_noexcept;
+mi_decl_nodiscard mi_decl_export void* mi_malloc_conceal(size_t size) mi_attr_noexcept;
+mi_decl_nodiscard mi_decl_export void* mi_calloc_conceal(size_t count, size_t size) mi_attr_noexcept;
+mi_decl_export void  mi_freezero(void* p, size_t size) mi_attr_noexcept;
 mi_decl_nodiscard mi_decl_export void* mi_aligned_recalloc(void* p, size_t newcount, size_t size, size_t alignment) mi_attr_noexcept;
 mi_decl_nodiscard mi_decl_export void* mi_aligned_offset_recalloc(void* p, size_t newcount, size_t size, size_t alignment, size_t offset) mi_attr_noexcept;
 

src/alloc-override.c

@@ -248,6 +248,9 @@ void* reallocarray(void* p, size_t count, size_t size)  { return mi_reallocarray
 int   reallocarr(void* p, size_t count, size_t size)    { return mi_reallocarr(p, count, size); }
 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); }
+void* malloc_conceal(size_t size)                       { return mi_malloc_conceal(size); }
+void* calloc_conceal(size_t count, size_t size)         { return mi_calloc_conceal(count, size); }
+void  freezero(void* p, size_t size)                    { mi_freezero(p, size); }
 
 #if defined(__GLIBC__) && defined(__linux__)
   // forward __libc interface (needed for glibc-based Linux distributions)

src/alloc.c

@@ -119,6 +119,49 @@ extern inline mi_decl_restrict void* mi_malloc(size_t size) mi_attr_noexcept {
   return mi_heap_malloc(mi_get_default_heap(), size);
 }
 
+mi_decl_restrict void* mi_malloc_conceal(size_t size) mi_attr_noexcept {
+  void* p;
+  p = mi_heap_malloc(mi_get_default_heap(), size);
+  if (mi_likely(p != NULL)) {
+#if defined(MADV_DONTDUMP)
+    madvise(p, size, MADV_DONTDUMP);
+#elif defined(MADV_NOCORE)
+    madvise(p, size, MADV_NOCORE);
+#endif
+  }
+  return p;
+}
+
+mi_decl_restrict void* mi_calloc_conceal(size_t count, size_t size) mi_attr_noexcept {
+  void* p;
+  p = mi_heap_calloc(mi_get_default_heap(),count,size);
+  if (mi_likely(p != NULL)) {
+#if defined(MADV_DONTDUMP)
+    madvise(p, size, MADV_DONTDUMP);
+#elif defined(MADV_NOCORE)
+    madvise(p, size, MADV_NOCORE);
+#endif
+  }
+  return p;
+}
+
+void mi_freezero(void* p, size_t size) mi_attr_noexcept {
+  mi_free(p);
+#if (MI_DEBUG==0)
+  if (size > 0) {
+#if defined(_MSC_VER)
+    SecureZeroMemory(p, size);
+#else
+    // reusing memset return value and using memory fence
+    // so memset call is generated regardless of the optimisation level
+    p = memset(p, 0, size);
+    __asm__ volatile("" :: "r"(p) : "memory");
+#endif
+  }
+#else
+  MI_UNUSED(size);
+#endif
+}
 
 void _mi_block_zero_init(const mi_page_t* page, void* p, size_t size) {
   // note: we need to initialize the whole usable block size to zero, not just the requested size,

test/test-api.c

@@ -98,6 +98,12 @@ int main(void) {
   CHECK_BODY("calloc0",{
     result = (mi_usable_size(mi_calloc(0,1000)) <= 16);
   });
+  CHECK_BODY("malloc_conceal",{
+    char* p = (char *)mi_malloc(24); 
+    p[0] = 1;
+    mi_freezero(p, 24);
+    result = p[0] == 0;
+  });
 
   // ---------------------------------------------------
   // Extended