Unable to override `new/delete` on macOS

[macrostring]

I was trying to use mimalloc debug mode to see statistics. Here's my simple test program.

#include <mimalloc-new-delete.h>
#include <mimalloc-override.h>

#include <vector>

int main() {
  std::vector<int, mi_stl_allocator<int>> vec(10000, 0);
  [[maybe_unused]] auto x = mi_new(1000);
  [[maybe_unused]] auto y = new int[1000];
  [[maybe_unused]] auto z = malloc(500);
}

The report is shown below. It seems that new operator is not overrided by mimalloc.

heap stats:     peak       total       freed     current        unit       count   
normal  20:   512   B     512   B       0         512   B     512   B       1        not all freed
normal  24:     1.0 KiB     1.0 KiB     0           1.0 KiB     1.0 KiB     1        not all freed
normal  45:    40.1 KiB    40.1 KiB    40.1 KiB     0          40.1 KiB     1        ok

heap stats:     peak       total       freed     current        unit       count   
    normal:    41.6 Ki     41.6 Ki     40.1 Ki      1.4 Ki     13.8 KiB     3        not all freed!
     large:     0           0           0           0                                ok
      huge:     0           0           0           0                                ok
     total:    41.6 KiB    41.6 KiB    40.1 KiB     1.4 KiB                          not all freed
malloc req:    40.6 KiB    40.6 KiB    39.2 KiB     1.4 KiB                          not all freed

  reserved:     1.0 GiB     1.0 GiB     0           1.0 GiB                          
 committed:     1.0 GiB     1.0 GiB     0           1.0 GiB                          
     reset:     0      
    purged:     0      
   touched:   232.9 KiB   232.9 KiB   160.6 KiB    72.2 KiB                          not all freed
  segments:     1           1           0           1                                not all freed!
-abandoned:     0           0           0           0                                ok
   -cached:     0           0           0           0                                ok
     pages:     3           3           1           2                                not all freed!
-abandoned:     0           0           0           0                                ok
 -extended:     3      
 -noretire:     1      
     mmaps:     2      
   commits:     0      
    resets:     0      
    purges:     0      
   threads:     0           0           0           0                                ok
  searches:     0.0 avg
numa nodes:     1
   elapsed:     0.000 s
   process: user: 0.014 s, system: 0.007 s, faults: 0, rss: 2.9 MiB, commit: 1.0 GiB

Compiling & Running:

clang++ -std=c++20 -Wall -Wextra -Wpedantic -fuse-ld=lld -Og t.cc -lmimalloc-debug -o t
env MIMALLOC_SHOW_STATS=1 DYLD_INSERT_LIBRARIES=/usr/local/lib/libmimalloc-debug.dylib ./t

Clang version:

Homebrew clang version 16.0.4
Target: x86_64-apple-darwin21.6.0
Thread model: posix
InstalledDir: /usr/local/opt/llvm/bin

System: macOS Monterey version 12.5 In addition, I compiled mimalloc with -DMI_OVERRIDE=OFF.

[W4RH4WK]

I've been struggling with a similar problem; Clang related but not on macOS.

Apparently, Clang has builtin functions for operator new / delete. When the builtin function is used, it bypasses any the mimalloc override.

Please try running your example with -fno-bultin to see whether this makes a difference? However, the bad news is that -fno-builtin will disable all of Clang's builtin functions. You probably don't want that. Furthermore, there does not seem to be a way of disabling builtin operator new / delete explicitly (src).

You could try -fno-builtin-malloc and -fno-builtin-free and see whether that works.

Edit: Also check the resulting binary using a disassembler. The compiler might remove allocations due to optimization.