configure hangs with --with-address-sanitizer on macOS (conftest spins in __asan::InitializeShadowMemory) #145199
Description
Bug report
Bug description:
When running ./configure --with-address-sanitizer on macOS, the configure step hangs at:
checking aligned memory access is required...
The generated conftest binary starts consuming ~90% CPU and never exits.
If I attach with lldb, the process appears to be spinning during AddressSanitizer initialization, with the stack showing:
__asan::InitializeShadowMemory
__asan::AsanInitInternal
wrap_malloc_default_zone
__malloc_init
libSystem_initializer
dyld4::prepare
...
It looks like this happens before main() is reached, so the hang seems to occur during ASAN runtime initialization (possibly during dyld/libSystem startup), rather than in cpython itself.
it can be reproduced after make distclean.
Environment:
macOS 26.3 (arm64)
xcode 26.2
Apple clang version 17.0.0 (clang-1700.6.3.2)
If this turns out to be a bug, I'd like to try working on it.
CPython versions tested on:
CPython main branch
Operating systems tested on:
macOS