gh-159320: use pthread_getattr_np for stack limit checks even on musl

[Yhg1s]

Adjust the use of pthread_getattr_np for stack size limit detection to avoid the problem on musl of it reporting the stack limit of the main thread incorrectly. On platforms where pthread_getattr_np underreports the main thread's stack size, use RLIMIT_STACK for the main thread instead. (Cross-compiles targeting musl will have to pass ac_cv_unreliable_pthread_getattr_np=yes to configure.)

• Issue: Broken stack size detection on Android #159320

[Yhg1s]

This is a more general fix than #159321, and incidentally also lets us have proper stack overflow protections on musl.

[Yhg1s]

For the record, I think this should not be backported.

[vstinner]

Can you please make the new "HAVE" macro private? Replace the macro in configure.ac:

-     [AC_DEFINE([HAVE_UNRELIABLE_PTHREAD_GETATTR_NP], [1],
+     [AC_DEFINE([_Py_HAVE_UNRELIABLE_PTHREAD_GETATTR_NP], [1],

Something like that:

Details

diff --git a/Python/ceval.c b/Python/ceval.c
index 3ed070a5846..e0623293670 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -65,7 +65,7 @@ _Py_ReachedRecursionLimitWithMargin(PyThreadState *tstate, int margin_count)
 #  define Py_C_STACK_SIZE 4000000
 #endif
 
-#ifdef HAVE_UNRELIABLE_PTHREAD_GETATTR_NP
+#ifdef _Py_HAVE_UNRELIABLE_PTHREAD_GETATTR_NP
 #ifdef HAVE_SYS_RESOURCE_H
 #  include <sys/resource.h>
 #endif
@@ -165,7 +165,7 @@ hardware_stack_limits(uintptr_t *base, uintptr_t *top, uintptr_t sp)
         err |= pthread_attr_destroy(&attr);
     }
     if (err == 0) {
-#    ifdef HAVE_UNRELIABLE_PTHREAD_GETATTR_NP
+#    ifdef _Py_HAVE_UNRELIABLE_PTHREAD_GETATTR_NP
         /* pthread_getattr_np on the main thread of a musl process reports a
          * stack size based on the current stack rather than RLIMIT_STACK.
          * New threads are reported correctly even on musl, so this fallback
diff --git a/Tools/build/check_capi_macros_ignored.txt b/Tools/build/check_capi_macros_ignored.txt
index cfa37c2b137..238c29b7039 100644
--- a/Tools/build/check_capi_macros_ignored.txt
+++ b/Tools/build/check_capi_macros_ignored.txt
@@ -627,7 +627,6 @@ HAVE_UNAME
 HAVE_UNISTD_H
 HAVE_UNLINKAT
 HAVE_UNLOCKPT
-HAVE_UNRELIABLE_PTHREAD_GETATTR_NP
 HAVE_UNSHARE
 HAVE_USABLE_WCHAR_T
 HAVE_UTIL_H
diff --git a/configure b/configure
index 221907add48..744ee2beef4 100755
--- a/configure
+++ b/configure
@@ -21875,7 +21875,7 @@ printf "%s\n" "$ac_cv_unreliable_pthread_getattr_np" >&6; }
    if test "x$ac_cv_unreliable_pthread_getattr_np" = xyes
 then :
 
-printf "%s\n" "#define HAVE_UNRELIABLE_PTHREAD_GETATTR_NP 1" >>confdefs.h
+printf "%s\n" "#define _Py_HAVE_UNRELIABLE_PTHREAD_GETATTR_NP 1" >>confdefs.h
 
 fi
 fi
diff --git a/configure.ac b/configure.ac
index e523314b492..42844ab64ca 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5620,7 +5620,7 @@ int main(void) {
       [ac_cv_unreliable_pthread_getattr_np=yes],
       [ac_cv_unreliable_pthread_getattr_np=no])])
    AS_VAR_IF([ac_cv_unreliable_pthread_getattr_np], [yes],
-     [AC_DEFINE([HAVE_UNRELIABLE_PTHREAD_GETATTR_NP], [1],
+     [AC_DEFINE([_Py_HAVE_UNRELIABLE_PTHREAD_GETATTR_NP], [1],
        [Define if pthread_getattr_np under-reports the main thread's stack size (musl behaviour).])])])
 
 # os.statx uses Linux's statx function.  AIX also has a function named statx,
diff --git a/pyconfig.h.in b/pyconfig.h.in
index 4193d536f3b..1fdeb7d9f2f 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -1706,10 +1706,6 @@
 /* Define to 1 if you have the 'unlockpt' function. */
 #undef HAVE_UNLOCKPT
 
-/* Define if pthread_getattr_np under-reports the main thread's stack size
-   (musl behaviour). */
-#undef HAVE_UNRELIABLE_PTHREAD_GETATTR_NP
-
 /* Define to 1 if you have the 'unshare' function. */
 #undef HAVE_UNSHARE
 
@@ -2227,6 +2223,10 @@
 /* Define if you have the 'tanpi' function. */
 #undef _Py_HAVE_TANPI
 
+/* Define if pthread_getattr_np under-reports the main thread's stack size
+   (musl behaviour). */
+#undef _Py_HAVE_UNRELIABLE_PTHREAD_GETATTR_NP
+
 /* Thread stack size set by the linker (in bytes). */
 #undef _Py_LINKER_THREAD_STACK_SIZE
 

[vstinner]

See also #159604 for FreeBSD.