fix: properly mark the C extension as safe for free-threading. #1799

https://github.com/python/cpython/blob/main/Doc/howto/free-threading-extensions.rst#c-api-extension-support-for-free-threading

Author: nedbat

.github/workflows/python-nightly.yml

@@ -86,11 +86,6 @@ jobs:
       - name: "Check out the repo"
         uses: "actions/checkout@v4"
 
-      - name: "Set PYTHON_GIL"
-        if: "${{ matrix.nogil }}"
-        run: |
-          echo "PYTHON_GIL=0" >> $GITHUB_ENV
-
       - name: "Install ${{ matrix.python-version }} with deadsnakes"
         uses: deadsnakes/action@6c8b9b82fe0b4344f4b98f2775fcc395df45e494
         if: "!startsWith(matrix.python-version, 'pypy-')"

coverage/ctracer/module.c

@@ -31,6 +31,10 @@ PyInit_tracer(void)
         return NULL;
     }
 
+#ifdef Py_GIL_DISABLED
+    PyUnstable_Module_SetGIL(mod, Py_MOD_GIL_NOT_USED);
+#endif
+
     if (CTracer_intern_strings() < 0) {
         return NULL;
     }