Class libmimalloc

tools/system_libs.py:1860–1917

class libmimalloc(MTLibrary):
  name = 'libmimalloc'

  cflags = [
    '-fno-builtin',
    '-Wno-unused-function',
    '-Wno-unused-but-set-variable',
    '-Wno-unused-variable',
    '-Wno-deprecated-pragma',
    # build emmalloc as only a system allocator, without exporting itself onto
    # malloc/free in the global scope
    '-DEMMALLOC_NO_STD_EXPORTS',
    # disable large pages by default, see:
    # https://github.com/microsoft/mimalloc/commit/9199d54bcf1e6dea0deb61a3a8a4b3ea4b45a341
    '-DMI_ENABLE_LARGE_PAGES=0',
    # halve the page size to 32KiB on wasm64 and to 16KiB on wasm32
    # https://github.com/microsoft/mimalloc/issues/647#issuecomment-1324109021
    # https://github.com/emscripten-core/emscripten/issues/20645#issuecomment-1962964755
    '-DMI_ARENA_SLICE_SHIFT=(12+MI_SIZE_SHIFT)',
    # `malloc`ed pointers must be aligned at least as strictly as max_align_t
    '-DMI_MAX_ALIGN_SIZE=8',
    # reserve memory in 64 MiB chunks (internally divided by 4)
    # Note: keep in sync with the -sINITIAL_HEAP default
    '-DMI_DEFAULT_ARENA_RESERVE=65536',
    # build mimalloc with an override of malloc/free
    '-DMI_MALLOC_OVERRIDE',
    # TODO: add build modes that include debug checks 1,2,3
    '-DMI_DEBUG=0',
    # disable `assert()` in the underlying emmalloc allocator
    '-DNDEBUG',
    # Emscripten uses musl libc internally
    '-DMI_LIBC_MUSL',
    # enable use of `__builtin_thread_pointer()`
    '-DMI_USE_BUILTIN_THREAD_POINTER',
  ]

  # malloc/free/calloc are runtime functions and can be generated during LTO
  # Therefore they cannot themselves be part of LTO.
  force_object_files = True

  includes = ['system/lib/mimalloc/include']

  # Build all of mimalloc, and also emmalloc which is used as the system
  # allocator underneath it.
  src_dir = 'system/lib/'
  src_files = glob_in_path(
    path='system/lib/mimalloc/src',
    glob_pattern='*.c',
    # mimalloc includes some files at the source level, so exclude them here.
    excludes={'alloc-override.c', 'free.c', 'page-queue.c', 'static.c'},
  )
  src_files += [utils.path_from_root('system/lib/mimalloc/src/prim/prim.c')]
  src_files += [utils.path_from_root('system/lib/emmalloc.c')]
  # Include sbrk.c in libc, it uses tracing and libc itself doesn't have a tracing variant.
  src_files += [utils.path_from_root('system/lib/libc/sbrk.c')]

  def can_use(self):
    return super().can_use() and settings.MALLOC == 'mimalloc'