gh-90815: Add mimalloc memory allocator (#109914)

* Add mimalloc v2.12

Modified src/alloc.c to remove include of alloc-override.c and not
compile new handler.

Did not include the following files:

 - include/mimalloc-new-delete.h
 - include/mimalloc-override.h
 - src/alloc-override-osx.c
 - src/alloc-override.c
 - src/static.c
 - src/region.c

mimalloc is thread safe and shares a single heap across all runtimes,
therefore finalization and getting global allocated blocks across all
runtimes is different.

* mimalloc: minimal changes for use in Python:

 - remove debug spam for freeing large allocations
 - use same bytes (0xDD) for freed allocations in CPython and mimalloc
   This is important for the test_capi debug memory tests

* Don't export mimalloc symbol in libpython.
* Enable mimalloc as Python allocator option.
* Add mimalloc MIT license.
* Log mimalloc in Lib/test/pythoninfo.py.
* Document new mimalloc support.
* Use macro defs for exports as done in:
  https://github.com/python/cpython/pull/31164/

Co-authored-by: Sam Gross <colesbury@gmail.com>
Co-authored-by: Christian Heimes <christian@python.org>
Co-authored-by: Victor Stinner <vstinner@python.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/Include/cpython/pymem.h b/Include/cpython/pymem.h
index dc4a65c..76b3221 100644
--- a/Include/cpython/pymem.h
+++ b/Include/cpython/pymem.h
@@ -23,6 +23,10 @@ typedef enum {
     PYMEM_ALLOCATOR_PYMALLOC = 5,
     PYMEM_ALLOCATOR_PYMALLOC_DEBUG = 6,
 #endif
+#ifdef WITH_MIMALLOC
+    PYMEM_ALLOCATOR_MIMALLOC = 7,
+    PYMEM_ALLOCATOR_MIMALLOC_DEBUG = 8,
+#endif
 } PyMemAllocatorName;