Fix "except+*" exception handling (GH-4013)

Fixes issue https://github.com/cython/cython/issues/3065
Fixes issue https://github.com/cython/cython/issues/3066

* delete cpp_exception_declaration_compatibility test
  Because I'm emitting an error at an earlier stage I don't think there's a way to get this test to work.

Cython/Compiler/ExprNodes.py

@@ -266,6 +266,20 @@ def translate_cpp_exception(code, pos, inside, py_result, exception_value, nogil
     code.putln(code.error_goto(pos))
     code.putln("}")
 
+def needs_cpp_exception_conversion(node):
+    assert node.exception_check == "+"
+    if node.exception_value is None:
+        return True
+    # exception_value can be a NameNode
+    # (in which case it's used as a handler function and no conversion is needed)
+    if node.exception_value.is_name:
+        return False
+    # or a CharNode with a value of "*"
+    if isinstance(node.exception_value, CharNode) and node.exception_value.value == "*":
+        return True
+    # Most other const-nodes are disallowed after "+" by the parser
+    return False
+
 
 # Used to handle the case where an lvalue expression and an overloaded assignment
 # both have an exception declaration.
@@ -3874,7 +3888,7 @@ class IndexNode(_IndexingBaseNode):
         if self.exception_check:
             if not setting:
                 self.is_temp = True
-            if self.exception_value is None:
+            if needs_cpp_exception_conversion(self):
                 env.use_utility_code(UtilityCode.load_cached("CppExceptionConversion", "CppSupport.cpp"))
         self.index = self.index.coerce_to(func_type.args[0].type, env)
         self.type = func_type.return_type
@@ -5958,7 +5972,7 @@ class SimpleCallNode(CallNode):
             env.use_utility_code(pyerr_occurred_withgil_utility_code)
         # C++ exception handler
         if func_type.exception_check == '+':
-            if func_type.exception_value is None:
+            if needs_cpp_exception_conversion(func_type):
                 env.use_utility_code(UtilityCode.load_cached("CppExceptionConversion", "CppSupport.cpp"))
 
         self.overflowcheck = env.directives['overflowcheck']
@@ -10279,7 +10293,7 @@ class UnopNode(ExprNode):
             self.exception_value = entry.type.exception_value
             if self.exception_check == '+':
                 self.is_temp = True
-                if self.exception_value is None:
+                if needs_cpp_exception_conversion(self):
                     env.use_utility_code(UtilityCode.load_cached("CppExceptionConversion", "CppSupport.cpp"))
         else:
             self.exception_check = ''
@@ -11232,7 +11246,7 @@ class BinopNode(ExprNode):
             # Used by NumBinopNodes to break up expressions involving multiple
             # operators so that exceptions can be handled properly.
             self.is_temp = 1
-            if self.exception_value is None:
+            if needs_cpp_exception_conversion(self):
                 env.use_utility_code(UtilityCode.load_cached("CppExceptionConversion", "CppSupport.cpp"))
         if func_type.is_ptr:
             func_type = func_type.base_type
@@ -12849,7 +12863,7 @@ class PrimaryCmpNode(ExprNode, CmpNode):
         self.exception_value = func_type.exception_value
         if self.exception_check == '+':
             self.is_temp = True
-            if self.exception_value is None:
+            if needs_cpp_exception_conversion(self):
                 env.use_utility_code(UtilityCode.load_cached("CppExceptionConversion", "CppSupport.cpp"))
         if len(func_type.args) == 1:
             self.operand2 = self.operand2.coerce_to(func_type.args[0].type, env)

Cython/Compiler/Nodes.py

@@ -627,8 +627,8 @@ class CFuncDeclaratorNode(CDeclaratorNode):
     # args             [CArgDeclNode]
     # templates        [TemplatePlaceholderType]
     # has_varargs      boolean
-    # exception_value  ConstNode
-    # exception_check  boolean    True if PyErr_Occurred check needed
+    # exception_value  ConstNode or NameNode    NameNode when the name of a c++ exception conversion function
+    # exception_check  boolean or "+"    True if PyErr_Occurred check needed, "+" for a c++ check
     # nogil            boolean    Can be called without gil
     # with_gil         boolean    Acquire gil around function body
     # is_const_method  boolean    Whether this is a const method
@@ -2512,8 +2512,15 @@ class CFuncDefNode(FuncDefNode):
                   "Function with optional arguments may not be declared public or api")
 
         if typ.exception_check == '+' and self.visibility != 'extern':
-            warning(self.cfunc_declarator.pos,
+            if typ.exception_value and typ.exception_value.is_name:
+                # it really is impossible to reason about what the user wants to happens
+                # if they've specified a C++ exception translation function. Therefore,
+                # raise an error.
+                error(self.cfunc_declarator.pos,
                     "Only extern functions can throw C++ exceptions.")
+            else:
+                warning(self.cfunc_declarator.pos,
+                    "Only extern functions can throw C++ exceptions.", 2)
 
         for formal_arg, type_arg in zip(self.args, typ.args):
             self.align_argument_type(env, type_arg)
@@ -2804,7 +2811,6 @@ class CFuncDefNode(FuncDefNode):
         if self.return_type.is_pyobject:
             return "0"
         else:
-            #return None
             return self.entry.type.exception_value
 
     def caller_will_check_exceptions(self):

tests/errors/cppexc_non_extern.pyx

+# mode: error
+# tag: warnings
+
+cdef inline void handle_exception():
+    pass
+
+# GH 3064 - cppfunc caused invalid code to be generated with +handle_exception
+# error to prevent this
+cdef test_func1(self) except +handle_exception:
+    pass
+
+# warning
+cdef test_func2(self) except +:
+    pass
+
+_ERRORS = """
+9:16: Only extern functions can throw C++ exceptions.
+"""
+
+_WARNINGS = """
+13:16: Only extern functions can throw C++ exceptions.
+"""

tests/run/cpp_exception_declaration_compatibility.srctree

-# tag: cpp
-
-"""
-PYTHON setup.py build_ext -i
-PYTHON test.py
-"""
-
-############### setup.py ###################
-from distutils.core import setup
-from Cython.Build import cythonize
-
-setup(
-    name="cython_test",
-    ext_modules=cythonize('*.pyx', language="c++")
-)
-
-
-############### test.py ###################
-
-from cpp_exc import TestClass
-
-TestClass().test_func()
-
-
-############### cpp_exc.pxd ###################
-
-cdef inline void handle_exception():
-    pass
-
-cdef class TestClass:
-    cpdef test_func(self) except +handle_exception
-
-
-############### cpp_exc.pyx ###################
-
-cdef class TestClass:
-    cpdef test_func(self) except +handle_exception:
-        print('test')

tests/run/cpp_exceptions_utility_code.pyx

+# mode: run
+# tag: cpp, werror
+# ticket: 3065
+
+# This is intentionally in a file on its own. The issue was that it failed to generate utility-code
+# and so putting it with the other c++ exception checks wouldn't be a useful test
+
+cdef extern from *:
+    """
+    #include <stdexcept>
+
+    void cppf(int raiseCpp) {
+        if (raiseCpp) {
+            throw std::runtime_error("cpp");
+        } else {
+            PyErr_SetString(PyExc_RuntimeError, "py");
+        }
+    }
+    """
+    void cppf(int) except+*
+
+
+def callcppf(int raiseCpp):
+    """
+    >>> callcppf(0)
+    py
+    >>> callcppf(1)
+    cpp
+    """
+    try:
+        cppf(raiseCpp)
+    except RuntimeError as e:
+        print(e.args[0])