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, 19 insertions, 0 deletions

diff --git a/Include/internal/pycore_mimalloc.h b/Include/internal/pycore_mimalloc.h
new file mode 100644
index 0000000..c29dc82
--- /dev/null
+++ b/Include/internal/pycore_mimalloc.h
@@ -0,0 +1,19 @@
+#ifndef Py_INTERNAL_MIMALLOC_H
+#define Py_INTERNAL_MIMALLOC_H
+
+#ifndef Py_BUILD_CORE
+#  error "this header requires Py_BUILD_CORE define"
+#endif
+
+#if defined(MIMALLOC_H) || defined(MIMALLOC_TYPES_H)
+#  error "pycore_mimalloc.h must be included before mimalloc.h"
+#endif
+
+#include "pycore_pymem.h"
+#define MI_DEBUG_UNINIT     PYMEM_CLEANBYTE
+#define MI_DEBUG_FREED      PYMEM_DEADBYTE
+#define MI_DEBUG_PADDING    PYMEM_FORBIDDENBYTE
+
+#include "mimalloc.h"
+
+#endif // Py_INTERNAL_MIMALLOC_H