Add PYTHONMALLOC env var

Issue #26516:

* Add PYTHONMALLOC environment variable to set the Python memory
  allocators and/or install debug hooks.
* PyMem_SetupDebugHooks() can now also be used on Python compiled in release
  mode.
* The PYTHONMALLOCSTATS environment variable can now also be used on Python
  compiled in release mode. It now has no effect if set to an empty string.
* In debug mode, debug hooks are now also installed on Python memory allocators
  when Python is configured without pymalloc.

1 files changed, 17 insertions, 8 deletions

diff --git a/Modules/main.c b/Modules/main.c
index ee129a5..b6dcdd0 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -93,14 +93,15 @@ static const char usage_5[] =
 "               The default module search path uses %s.\n"
 "PYTHONCASEOK : ignore case in 'import' statements (Windows).\n"
 "PYTHONIOENCODING: Encoding[:errors] used for stdin/stdout/stderr.\n"
-"PYTHONFAULTHANDLER: dump the Python traceback on fatal errors.\n\
-";
-static const char usage_6[] = "\
-PYTHONHASHSEED: if this variable is set to 'random', a random value is used\n\
-   to seed the hashes of str, bytes and datetime objects.  It can also be\n\
-   set to an integer in the range [0,4294967295] to get hash values with a\n\
-   predictable seed.\n\
-";
+"PYTHONFAULTHANDLER: dump the Python traceback on fatal errors.\n";
+static const char usage_6[] =
+"PYTHONHASHSEED: if this variable is set to 'random', a random value is used\n"
+"   to seed the hashes of str, bytes and datetime objects.  It can also be\n"
+"   set to an integer in the range [0,4294967295] to get hash values with a\n"
+"   predictable seed.\n"
+"PYTHONMALLOC: set the Python memory allocators and/or install debug hooks\n"
+"   on Python memory allocators. Use PYTHONMALLOC=debug to install debug\n"
+"   hooks.\n";
 
 static int
 usage(int exitcode, const wchar_t* program)
@@ -341,6 +342,7 @@ Py_Main(int argc, wchar_t **argv)
     int help = 0;
     int version = 0;
     int saw_unbuffered_flag = 0;
+    char *opt;
     PyCompilerFlags cf;
     PyObject *warning_option = NULL;
     PyObject *warning_options = NULL;
@@ -365,6 +367,13 @@ Py_Main(int argc, wchar_t **argv)
         }
     }
 
+    opt = Py_GETENV("PYTHONMALLOC");
+    if (_PyMem_SetupAllocators(opt) < 0) {
+        fprintf(stderr,
+                "Error in PYTHONMALLOC: unknown allocator \"%s\"!\n", opt);
+        exit(1);
+    }
+
     Py_HashRandomizationFlag = 1;
     _PyRandom_Init();