Do not limit the address space where it cannot work

AddressSanitizer reserves terabytes of address space for its shadow memory,
so any limit stops the interpreter from starting.

macOS reserves much more address space than Linux does, so 512 MiB is not
enough of a margin there.

Author: serhiy-storchaka

Lib/test/support/__init__.py

@@ -1276,14 +1276,19 @@ def _limit_address_space(nbytes):
     A test which uses much more memory than it declares then fails with a
     MemoryError instead of making the machine swap.
     """
+    if check_sanitizer(address=True):
+        # AddressSanitizer reserves terabytes of address space for its shadow
+        # memory, so any limit stops the interpreter from starting.
+        return
     try:
         import resource
         rlimit = resource.RLIMIT_AS
     except (ImportError, AttributeError):
         return
     # The margin does not grow with the declared size: the interpreter itself
-    # reserves about 250 MiB, whatever the test asks for.
-    limit = int(nbytes) + 512 * _1M
+    # reserves about 250 MiB, whatever the test asks for.  macOS reserves more.
+    margin = _1G if sys.platform == 'darwin' else 512 * _1M
+    limit = int(nbytes) + margin
     soft, hard = resource.getrlimit(rlimit)
     for current in soft, hard:
         if current != resource.RLIM_INFINITY:

Misc/NEWS.d/next/Tests/2026-08-18-19-36-04.gh-issue-75876.5AhLHL.rst

@@ -1,5 +1,5 @@
 A test decorated with :func:`~test.support.bigmemtest` now runs with the
-address space limited to what it declares plus 512 MiB, so that a test which
+address space limited to what it declares plus a margin, so that a test which
 uses much more memory than it declares fails instead of making the machine
 swap.  Pass ``limit_address_space=False`` for a test which reserves much more
 address space than it uses.