python_bindings: acquire GIL before printing

python_bindings/correctness/realize_warnings.py

@@ -0,0 +1,28 @@
+import halide as hl
+from io import StringIO
+from contextlib import redirect_stdout
+
+
+def test_warnings():
+    i = hl.Var()
+    f = hl.Func("f")
+    f[i] = 0.0
+    f.bound(i, 0, 127)
+
+    g = hl.Func("g")
+    g[i] = f[i * i]
+
+    expected_warning = "Warning: It is meaningless to bound dimension v0 of function f to be within [0, 127] because " \
+                       "the function is scheduled inline.\n"
+
+    buffer = StringIO()
+    with redirect_stdout(buffer):
+        g.realize([16])
+
+    buffer.seek(0)
+    stdout_lines = buffer.readlines()
+    assert stdout_lines == [expected_warning] * 3
+
+
+if __name__ == '__main__':
+    test_warnings()

python_bindings/src/PyError.cpp

@@ -17,7 +17,7 @@ void halide_python_print(JITUserContext *, const char *msg) {
 class HalidePythonCompileTimeErrorReporter : public CompileTimeErrorReporter {
 public:
     void warning(const char *msg) override {
-        py::print(msg, py::arg("end") = "");
+        halide_python_print(nullptr, msg);
     }
 
     void error(const char *msg) override {