From: Victor Stinner <vstinner@python.org>
Date: Wed, 17 Jun 2026 08:23:57 +0000 (+0200)
Subject: gh-151546: Fix stack limits on musl (#151548)
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9a61d1c0c8ebe21277c0a84abf6000049540464f;p=thirdparty%2FPython%2Fcpython.git

gh-151546: Fix stack limits on musl (#151548)

If the thread stack size is set by linker flags, pass the stack size
to Python/ceval.c via the new _Py_LINKER_THREAD_STACK_SIZE variable
to set Py_C_STACK_SIZE macro.
---

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-06-16-17-23-37.gh-issue-151546.LhiaZz.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-16-17-23-37.gh-issue-151546.LhiaZz.rst
new file mode 100644
index 000000000000..af1c23bd5035
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-06-16-17-23-37.gh-issue-151546.LhiaZz.rst
@@ -0,0 +1,3 @@
+Fix the stack limit check if Python is linked to musl (ex: Alpine Linux).
+Use the stack size set by the linker to compute the stack limits. Patch by
+Victor Stinner.
diff --git a/Python/ceval.c b/Python/ceval.c
index a9b31affca98..d6dd7f9a82c4 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -49,7 +49,9 @@ _Py_ReachedRecursionLimitWithMargin(PyThreadState *tstate, int margin_count)
 #endif
 }
 
-#if defined(__s390x__)
+#if defined(_Py_LINKER_THREAD_STACK_SIZE)
+#  define Py_C_STACK_SIZE _Py_LINKER_THREAD_STACK_SIZE
+#elif defined(__s390x__)
 #  define Py_C_STACK_SIZE 320000
 #elif defined(_WIN32)
    // Don't define Py_C_STACK_SIZE, ask the O/S
diff --git a/configure b/configure
index 7608a0493b0e..7408fac738b8 100755
--- a/configure
+++ b/configure
@@ -9927,6 +9927,10 @@ printf "%s\n" "$ac_cv_thread_stack_size" >&6; }
 
     if test "$ac_cv_thread_stack_size" != "default" -a "$ac_cv_thread_stack_size" != "unknown"; then
         LDFLAGS="$LDFLAGS -Wl,-z,stack-size=$ac_cv_thread_stack_size"
+        # Stack size used by Python/ceval.c to set Py_C_STACK_SIZE
+
+printf "%s\n" "#define _Py_LINKER_THREAD_STACK_SIZE $ac_cv_thread_stack_size" >>confdefs.h
+
     fi
 fi
 
diff --git a/configure.ac b/configure.ac
index 020861b4c823..dbc781b545dd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2507,6 +2507,9 @@ EOF
 
     if test "$ac_cv_thread_stack_size" != "default" -a "$ac_cv_thread_stack_size" != "unknown"; then
         LDFLAGS="$LDFLAGS -Wl,-z,stack-size=$ac_cv_thread_stack_size"
+        # Stack size used by Python/ceval.c to set Py_C_STACK_SIZE
+        AC_DEFINE_UNQUOTED([_Py_LINKER_THREAD_STACK_SIZE], [$ac_cv_thread_stack_size],
+                  [Thread stack size set by the linker (in bytes).])
     fi
 fi
 
diff --git a/pyconfig.h.in b/pyconfig.h.in
index dc2404fe85fa..999a55a5efd0 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -2088,6 +2088,9 @@
 /* Define if you have the 'PR_SET_VMA_ANON_NAME' constant. */
 #undef _Py_HAVE_PR_SET_VMA_ANON_NAME
 
+/* Thread stack size set by the linker (in bytes). */
+#undef _Py_LINKER_THREAD_STACK_SIZE
+
 /* Define to 1 if the machine stack grows down (default); 0 if it grows up. */
 #undef _Py_STACK_GROWS_DOWN