Allow print statements in nogil sections.

Would be nice to allow this also for the print() function, but that's tricky because we have to insert the "GILStatNode" before analysing the declarations, which is when we learn if it's really the builtin print function or something else.

Cython/Compiler/ParseTreeTransforms.py

@@ -2842,20 +2842,21 @@ class InjectGilHandling(VisitorTransform, SkipDeclarations):
     Must run before the AnalyseDeclarationsTransform to make sure the GILStatNodes get
     set up, parallel sections know that the GIL is acquired inside of them, etc.
     """
-    def __call__(self, root):
-        self.nogil = False
-        return super(InjectGilHandling, self).__call__(root)
+    nogil = False
 
     # special node handling
 
-    def visit_RaiseStatNode(self, node):
-        """Allow raising exceptions in nogil sections by wrapping them in a 'with gil' block."""
+    def _inject_gil_in_nogil(self, node):
+        """Allow the (Python statement) node in nogil sections by wrapping it in a 'with gil' block."""
         if self.nogil:
             node = Nodes.GILStatNode(node.pos, state='gil', body=node)
         return node
 
+    visit_RaiseStatNode = _inject_gil_in_nogil
+    visit_PrintStatNode = _inject_gil_in_nogil  # sadly, not the function
+
     # further candidates:
-    # def visit_AssertStatNode(self, node):
+    # def visit_AssertStatNode(self, node):  # -> try to keep the condition GIL-free if possible
     # def visit_ReraiseStatNode(self, node):
 
     # nogil tracking

tests/errors/nogil.pyx

@@ -52,7 +52,7 @@ cdef object m():
         x, y = y, x
         obj[i] = x
         obj.fred = x
-        print obj
+        print obj  # allowed!
         del fred
         return obj
         raise obj  # allowed!
@@ -151,10 +151,10 @@ _ERRORS = u"""
 53:11: Indexing Python object not allowed without gil
 54:11: Accessing Python attribute not allowed without gil
 54:11: Assignment of Python object not allowed without gil
-55:8: Constructing Python tuple not allowed without gil
-55:8: Python print statement not allowed without gil
+
 56:8: Deleting Python object not allowed without gil
 57:8: Returning Python object not allowed without gil
+
 59:11: Truth-testing Python object not allowed without gil
 61:14: Truth-testing Python object not allowed without gil
 63:8: For-loop using object bounds or target not allowed without gil

tests/run/with_gil_automatic.pyx

+# mode: run
+# tag: nogil
+# cython: language_level=2
+
+cimport cython
+
+
+@cython.test_assert_path_exists(
+    "//GILStatNode",
+    "//GILStatNode//GILStatNode",
+    "//GILStatNode//GILStatNode//PrintStatNode",
+)
+def test_print_in_nogil(x):
+    """
+    >>> test_print_in_nogil(123)
+    --123--
+    """
+    with nogil:
+        print f"--{x}--"
+
+
+@cython.test_assert_path_exists(
+    "//GILStatNode",
+    "//GILStatNode//GILStatNode",
+    "//GILStatNode//GILStatNode//RaiseStatNode",
+)
+def test_raise_in_nogil(x):
+    """
+    >>> try: test_raise_in_nogil(123)
+    ... except ValueError as exc: print(exc)
+    ... else: print("NOT RAISED !")
+    --123--
+    """
+    with nogil:
+        raise ValueError(f"--{x}--")