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gh-148260: Use at least 1 MiB stack size on musl #149993

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gh-148260: Use at least 1 MiB stack size on musl #149993

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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Build/2026-05-18-16-00-41.gh-issue-148260.UwFiIX.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
On Linux when Python is linked to the musl C library, use a thread stack
size of at least 1 MiB instead of musl default which is 128 kiB. Patch by
Victor Stinner.
52 changes: 52 additions & 0 deletions configure
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45 changes: 45 additions & 0 deletions configure.ac
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Expand Up @@ -2462,6 +2462,51 @@ AS_CASE([$ac_sys_system],
]
)

dnl On Linux, check the thread stack size. musl (ex: Alpine Linux) uses
dnl a default thread stack size of 128 kB, whereas the glibc uses 8 MiB.
dnl Python uses at least 1 MiB.
if test "$ac_sys_system" = "Linux" -a "$cross_compiling" = no; then
AC_CACHE_CHECK([for thread stack size], [ac_cv_thread_stack_size], [
cat > conftest.c <<EOF
#include <pthread.h>

int main()
{
pthread_attr_t attrs;
size_t size;

int rc = pthread_attr_init(&attrs);
if (rc != 0) {
return 2;
}

rc = pthread_attr_getstacksize(&attrs, &size);
if (rc != 0) {
return 2;
}

if (size < 1024 * 1024) {
return 1;
}
return 0;
}
EOF

ac_cv_thread_stack_size="default"
if $CC -pthread $CFLAGS conftest.c -o conftest &>/dev/null; then
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@vstinner vstinner May 18, 2026

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I chose to use $CC -pthread to make sure that the pthread API can be used in the C program. We check if -pthread is supported above, near line 3064, which sets CC="$CC -pthread" if the flag is supported. I should maybe omit -pthread and move my code after the -pthread check.

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@Yhg1s Yhg1s May 18, 2026

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I think using -pthread explicitly is fine, it doesn't matter if it's passed to the compiler twice.

./conftest &>/dev/null
if test $? -eq 1; then
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@Yhg1s Yhg1s May 18, 2026

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For debugging it would probably be nice if the output said whether the stack size is good enough, needs overriding or just unknown (return code 2)

ac_cv_thread_stack_size=1048576
fi
fi
rm -f conftest.c conftest
])

if test "$ac_cv_thread_stack_size" != "default"; then
LDFLAGS="$LDFLAGS -Wl,-z,stack-size=$ac_cv_thread_stack_size"
fi
fi

AS_CASE([$enable_wasm_dynamic_linking],
[yes], [ac_cv_func_dlopen=yes],
[no], [ac_cv_func_dlopen=no],
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