add MI_FREE_IS_CHECKED option; shared libraries always check pointers in free now (see PR #1285)

Author: daanx

CMakeLists.txt

@@ -13,6 +13,7 @@ option(MI_GUARDED           "Build with guard pages behind certain object alloca
 option(MI_USE_CXX           "Use the C++ compiler to compile the library (instead of the C compiler)" OFF)
 option(MI_OPT_ARCH          "Only for optimized builds: turn on architecture specific optimizations (for x64: '-march=haswell;-mavx2' (2013), for arm64: '-march=armv8.1-a' (2016))" OFF)
 option(MI_OPT_SIMD          "Use SIMD instructions (requires MI_OPT_ARCH to be enabled)" OFF)
+option(MI_FREE_IS_CHECKED   "Always check for invalid pointers in 'free' (always enabled in debug and secure builds, or when MI_OVERRIDE is ON)" OFF)
 
 option(MI_DEBUG             "Enable assertion checks (enabled by default in a debug build)" OFF)
 option(MI_DEBUG_INTERNAL    "Enable assertion and internal invariant checks (enabled by default in a debug build)" OFF)
@@ -378,6 +379,17 @@ else()
   endif()
 endif()
 
+if(MI_DEBUG OR MI_SECURE)
+  set(MI_FREE_IS_CHECKED ON)
+endif()
+if(MI_FREE_IS_CHECKED)
+  message(STATUS "Check validity of pointers passed to 'mi_free' (MI_FREE_IS_CHECKED=ON)")
+  list(APPEND mi_defines MI_FREE_IS_CHECKED=1)
+elseif(MI_OVERRIDE)  
+  message(STATUS "Check validity of pointers passed to 'mi_free' only in the dynamic link library (MI_OVERRIDE=ON, MI_FREE_IS_CHECKED=OFF)")
+  list(APPEND mi_cflags_dynamic -DMI_FREE_IS_CHECKED=1)
+endif()
+
 if(MI_XMALLOC)
   message(STATUS "Enable abort() calls on memory allocation failure (MI_XMALLOC=ON)")
   list(APPEND mi_defines MI_XMALLOC=1)

include/mimalloc/internal.h

@@ -667,7 +667,7 @@ static inline mi_page_t* _mi_checked_ptr_page(const void* p) {
 
 static inline mi_page_t* _mi_ptr_page(const void* p) {
   mi_assert_internal(p==NULL || mi_is_in_heap_region(p));
-  #if MI_DEBUG || MI_SECURE || defined(__APPLE__)
+  #if MI_DEBUG || MI_SECURE || MI_FREE_IS_CHECKED
   return _mi_checked_ptr_page(p);
   #else
   return _mi_unchecked_ptr_page(p);