From 2ef7f6e3d92abcd5db409c76e6d5fc5fa5b3b890 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Wed, 17 Jun 2026 11:13:40 +0200
Subject: [PATCH] [3.15] gh-151546: Fix stack limits on musl (#151548)
 (#151583)

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.

(cherry picked from commit 9a61d1c0c8ebe21277c0a84abf6000049540464f)
(cherry picked from commit a5c5edddbc3ca7192c057f65fb3a8ff4ea360f96)
---
 .../2026-06-16-17-23-37.gh-issue-151546.LhiaZz.rst            | 3 +++
 Python/ceval.c                                                | 4 +++-
 configure                                                     | 4 ++++
 configure.ac                                                  | 3 +++
 pyconfig.h.in                                                 | 3 +++
 5 files changed, 16 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-06-16-17-23-37.gh-issue-151546.LhiaZz.rst

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 000000000000000..af1c23bd50355f2
--- /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 377b4644eddd2a8..b4fded923c10d3f 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -366,7 +366,9 @@ _Py_EnterRecursiveCallUnchecked(PyThreadState *tstate)
     }
 }
 
-#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 055ecb3b97156ea..a03bca2e1f92cbd 100755
--- a/configure
+++ b/configure
@@ -9839,6 +9839,10 @@ 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 caf7e88d7f27605..80a3854ce672ea9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2470,6 +2470,9 @@ 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 9502fcebf5d7802..3ed77cb7f064549 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -2023,6 +2023,9 @@
 /* HACL* library can compile SIMD256 implementations */
 #undef _Py_HACL_CAN_COMPILE_VEC256
 
+/* 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