bpo-47162: Add call trampoline to mitigate bad fpcasts on Emscripten (GH-32189)

3 files changed, 20 insertions, 6 deletions

diff --git a/Python/import.c b/Python/import.c
index 982ec8c..4b6d6d1 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -527,7 +527,7 @@ import_find_extension(PyThreadState *tstate, PyObject *name,
     else {
         if (def->m_base.m_init == NULL)
             return NULL;
-        mod = def->m_base.m_init();
+        mod = _PyImport_InitFunc_TrampolineCall(def->m_base.m_init);
         if (mod == NULL)
             return NULL;
         if (PyObject_SetItem(modules, name, mod) == -1) {
@@ -958,6 +958,13 @@ PyImport_GetImporter(PyObject *path)
     return get_path_importer(tstate, path_importer_cache, path_hooks, path);
 }
 
+#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
+#include <emscripten.h>
+EM_JS(PyObject*, _PyImport_InitFunc_TrampolineCall, (PyModInitFunction func), {
+    return wasmTable.get(func)();
+});
+#endif // __EMSCRIPTEN__ && PY_CALL_TRAMPOLINE
+
 static PyObject*
 create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
 {
@@ -973,8 +980,7 @@ create_builtin(PyThreadState *tstate, PyObject *name, PyObject *spec)
                 /* Cannot re-init internal module ("sys" or "builtins") */
                 return PyImport_AddModuleObject(name);
             }
-
-            mod = (*p->initfunc)();
+            mod = _PyImport_InitFunc_TrampolineCall(*p->initfunc);
             if (mod == NULL) {
                 return NULL;
             }
diff --git a/Python/importdl.c b/Python/importdl.c
index f66c601..870ae27 100644
--- a/Python/importdl.c
+++ b/Python/importdl.c
@@ -102,7 +102,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
     const char *oldcontext;
     dl_funcptr exportfunc;
     PyModuleDef *def;
-    PyObject *(*p0)(void);
+    PyModInitFunction p0;
 
     name_unicode = PyObject_GetAttrString(spec, "name");
     if (name_unicode == NULL) {
@@ -157,7 +157,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
         goto error;
     }
 
-    p0 = (PyObject *(*)(void))exportfunc;
+    p0 = (PyModInitFunction)exportfunc;
 
     /* Package context is needed for single-phase init */
     oldcontext = _Py_PackageContext;
@@ -166,7 +166,7 @@ _PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *fp)
         _Py_PackageContext = oldcontext;
         goto error;
     }
-    m = p0();
+    m = _PyImport_InitFunc_TrampolineCall(p0);
     _Py_PackageContext = oldcontext;
 
     if (m == NULL) {
diff --git a/Python/importdl.h b/Python/importdl.h
index 9847652..26d18b6 100644
--- a/Python/importdl.h
+++ b/Python/importdl.h
@@ -10,6 +10,14 @@ extern const char *_PyImport_DynLoadFiletab[];
 
 extern PyObject *_PyImport_LoadDynamicModuleWithSpec(PyObject *spec, FILE *);
 
+typedef PyObject *(*PyModInitFunction)(void);
+
+#if defined(__EMSCRIPTEN__) && defined(PY_CALL_TRAMPOLINE)
+extern PyObject *_PyImport_InitFunc_TrampolineCall(PyModInitFunction func);
+#else
+#define _PyImport_InitFunc_TrampolineCall(func) (func)()
+#endif
+
 /* Max length of module suffix searched for -- accommodates "module.slb" */
 #define MAXSUFFIXSIZE 12