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MallocScribble is available as "opt.junk" in jemalloc [1]. As for guard pages, tcmalloc has TCMALLOC_PAGE_FENCE [2], and there is an issue [3] in jemalloc. In

MallocScribble is available as "opt.junk" in jemalloc [1]. As for guard pages, tcmalloc has TCMALLOC_PAGE_FENCE [2], and there is an issue [3] in jemalloc. In any case, Apple and others have invested hugely in LLVM AddressSanitizer, so the Electric Fence-like malloc debugging features are considered more of a last resort these days. [1]: http://jemalloc.net/jemalloc.3.html http://jemalloc.net/jemalloc.3.html [2]: https://chromium.googlesource.com/external/gperftools/+/gperftools-2.2.1/src/debugallocation.cc https://chromium.googlesource.com/external/gperftools/+/gper... [3]: https://github.com/jemalloc/jemalloc/issues/1664 https://github.com/jemalloc/jemalloc/issues/1664

1over137 5y ago
Yeah, but ASan requires recompilation. GuardMalloc and MallocScribble apply to your whole process, and so even malloc()s called by system frameworks (ex AppKit) get checked. I've found several OS bugs this way over the years. Maybe internally Apple has ASan builds of the whole OS, but they don't distribute it externally.
- pcwalton 5y ago
  Valgrind works OK on macOS, right?
  - lukeh 5y ago
    According to release notes, it supports 10.12 (with preliminary support for 10.13). That's several releases behind (10.14, 10.15, 11, 12).
  - jcelerier 5y ago
    it hasn't for years afaik
  - 1over137 5y ago
    Homebrew won't even install valgrind anymore.
- saagarjha 5y ago
  Security-critical components like the kernel and WebKit have ASan variants, that’s for sure. But they also use custom allocators.
vlovich123 5y ago
When I worked at Apple they were the first resort as they were usually cheaper to iterate with (no recompilation, lower overhead, etc), but ASAN has only gotten better & was the primary focus. I agree that maybe jemalloc might be a good drop-in replacement, but it just might not be a priority for the libc maintainers. Lots of low hanging fruit can be missed for very long periods of time because you have to pick what to focus on. GWP ASAN from TCMalloc might be the better direction for runtime support for memory corruption from malloc as it gives a lot of ASAN-like protection with an electric fence-like performance profile (& can be turned on/off at runtime).
saagarjha 5y ago
Apple has a whole set of heap debugging tools that they use internally and are quite useful even as a third party developer, and I’m sure they rely on having certain heap metadata around so they can reconstruct a memory graph after the fact. Take a look at heap(1) and leaks(1) to see what they offer.

1over137 5y ago

Yeah, but ASan requires recompilation. GuardMalloc and MallocScribble apply to your whole process, and so even malloc()s called by system frameworks (ex AppKit) get checked. I've found several OS bugs this way over the years. Maybe internally Apple has ASan builds of the whole OS, but they don't distribute it externally.

pcwalton 5y ago
Valgrind works OK on macOS, right?
- lukeh 5y ago
  According to release notes, it supports 10.12 (with preliminary support for 10.13). That's several releases behind (10.14, 10.15, 11, 12).
- jcelerier 5y ago
  it hasn't for years afaik
- 1over137 5y ago
  Homebrew won't even install valgrind anymore.
saagarjha 5y ago
Security-critical components like the kernel and WebKit have ASan variants, that’s for sure. But they also use custom allocators.

vlovich123 5y ago

When I worked at Apple they were the first resort as they were usually cheaper to iterate with (no recompilation, lower overhead, etc), but ASAN has only gotten better & was the primary focus. I agree that maybe jemalloc might be a good drop-in replacement, but it just might not be a priority for the libc maintainers. Lots of low hanging fruit can be missed for very long periods of time because you have to pick what to focus on. GWP ASAN from TCMalloc might be the better direction for runtime support for memory corruption from malloc as it gives a lot of ASAN-like protection with an electric fence-like performance profile (& can be turned on/off at runtime).

saagarjha 5y ago

Apple has a whole set of heap debugging tools that they use internally and are quite useful even as a third party developer, and I’m sure they rely on having certain heap metadata around so they can reconstruct a memory graph after the fact. Take a look at heap(1) and leaks(1) to see what they offer.