[3.15] gh-154874: Fix the sign of curses.termattrs() (GH-154875)

fedonman · cursoragent · sankalpsthakur · commit e5cf9684c216 · 2026-08-11T15:16:55.000+05:30
termattrs() returns a chtype mask, but it was routed through an int, so a terminal that advertises A_ITALIC came back negative and the result could no longer be passed to the attribute functions. (cherry picked from commit 0b083c4) Co-authored-by: Vyron Vasileiadis <hi@fedonman.com> Signed-off-by: Sankalp Thakur <sankalphimself@gmail.com> Co-authored-by: Cursor <cursoragent@cursor.com>
diff --git a/Lib/test/test_curses.py b/Lib/test/test_curses.py
@@ -1023,6 +1023,20 @@ def test_env_queries(self):
         self.assertIsInstance(c, bytes)
         self.assertEqual(len(c), 1)
 
+    def test_termattrs_is_not_negative(self):
+        # A_ITALIC is the topmost bit of a 32-bit attribute mask, so termattrs()
+        # only tells a signed result from an unsigned one on a terminal that
+        # advertises it.  3.15 lacks the newterm()/pty harness used on main, so
+        # exercise the current screen: skip when the top bit is not advertised.
+        attrs = curses.termattrs()
+        italic = getattr(curses, 'A_ITALIC', 0)
+        if not italic or not attrs & italic:
+            self.skipTest('the terminal advertises no attribute in the top bit')
+        self.assertGreaterEqual(attrs, 0)
+        # termattrs() exists to be passed back to the attribute functions,
+        # which reject a negative mask.
+        self.stdscr.attrset(attrs)
+
     def test_output_options(self):
         stdscr = self.stdscr
 
diff --git a/Misc/NEWS.d/next/Library/2026-07-29-11-58-17.gh-issue-154874.NAPdBp.rst b/Misc/NEWS.d/next/Library/2026-07-29-11-58-17.gh-issue-154874.NAPdBp.rst
@@ -0,0 +1,3 @@
+Fix :func:`curses.termattrs` returning a negative value on a terminal that
+supports :const:`curses.A_ITALIC`, which left its result unusable as an
+attribute mask.
diff --git a/Modules/_cursesmodule.c b/Modules/_cursesmodule.c
@@ -4959,7 +4959,11 @@ Return a logical OR of all video attributes supported by the terminal.
 static PyObject *
 _curses_termattrs_impl(PyObject *module)
 /*[clinic end generated code: output=b06f437fce1b6fc4 input=0559882a04f84d1d]*/
-NoArgReturnIntFunctionBody(termattrs)
+{
+    PyCursesStatefulInitialised(module);
+
+    return PyLong_FromUnsignedLong((unsigned long)(chtype)termattrs());
+}
 
 /*[clinic input]
 @permit_long_summary

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	+Fix :func:`curses.termattrs` returning a negative value on a terminal that
	`2`	+supports :const:`curses.A_ITALIC`, which left its result unusable as an
	`3`	`+attribute mask.`