We're failing some tests in CI due to recursion depth issues

Which are quite hard to reproduce because they depend on the details
of the C stack.

Anyway, we should probably start using the recursion-depth-tracking functions
in more place, rather than getting segfaults.  There are a lot of CPython tests
that test for recursion-depth-checking.

src/core/types.h

@@ -1116,6 +1116,22 @@ public:
     operator FILE*() const { return file; }
 };
 
+void throwCAPIException();
+// A C++-style RAII way of doing Py_EnterRecursiveCall + Py_LeaveRecursiveCall
+class _RecursiveBlockHelper {
+public:
+    ~_RecursiveBlockHelper() { Py_LeaveRecursiveCall(); }
+};
+#define RECURSIVE_BLOCK(S, reason)                                                                                     \
+    _RecursiveBlockHelper CAT(_recursive_helper, __LINE__);                                                            \
+    if (Py_EnterRecursiveCall(reason)) {                                                                               \
+        if (S == CAPI)                                                                                                 \
+            return NULL;                                                                                               \
+        else                                                                                                           \
+            throwCAPIException();                                                                                      \
+    }
+
+
 // similar to Java's Array.binarySearch:
 // return values are either:
 //   >= 0 : the index where a given item was found

src/runtime/capi.cpp

@@ -539,7 +539,7 @@ extern "C" int Py_FlushLine(void) noexcept {
     return PyFile_WriteString("\n", f);
 }
 
-void setCAPIException(STOLEN(const ExcInfo&) e) {
+void setCAPIException(STOLEN(const ExcInfo&) e) noexcept {
     PyErr_Restore(e.type, e.value, e.traceback);
 }
 

src/runtime/objmodel.cpp

@@ -4747,6 +4747,9 @@ Box* callFunc(BoxedFunctionBase* func, CallRewriteArgs* rewrite_args, ArgPassSpe
 template <ExceptionStyle S>
 static Box* callChosenCF(CompiledFunction* chosen_cf, BoxedClosure* closure, BoxedGenerator* generator, Box* globals,
                          Box* oarg1, Box* oarg2, Box* oarg3, Box** oargs) noexcept(S == CAPI) {
+    // TODO: this should be done in the rewrite as well
+    RECURSIVE_BLOCK(S, " in function call");
+
     if (S != chosen_cf->exception_style) {
         if (S == CAPI) {
             try {

src/runtime/types.h

@@ -169,7 +169,7 @@ void checkAndThrowCAPIException();
 void throwCAPIException() __attribute__((noreturn));
 void ensureCAPIExceptionSet();
 struct ExcInfo;
-void setCAPIException(STOLEN(const ExcInfo&) e);
+void setCAPIException(STOLEN(const ExcInfo&) e) noexcept;
 
 // Finalizer-related
 void dealloc_null(Box* box);

test/CPYTHON_TEST_NOTES.md

@@ -172,7 +172,7 @@ test_unicode            argument passing issue?
 test_userdict           segfault: repr of recursive dict?
 test_userlist           slice(1L, 1L)
 test_userstring         float(1L); hangs in test_replace
-test_warnings           [unknown]
+test_warnings           Among other things, we don't support the -W flag
 test_weakref            weird function-picking bug (something around float.__add__), plase also fix the weakref issue in test_abc
 test_winreg             [unknown]
 test_winsound           [unknown]

test/cpython/warning_tests.py

+../../from_cpython/Lib/test/warning_tests.py
\ No newline at end of file