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fix: avoid casting warnings for unnamed parameters before multiline bodies #483

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fix: avoid casting warnings for unnamed parameters before multiline bodies #483

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1ff138c
fix: avoid casting warnings for unnamed parameters before multiline b…
DanceoftheAurora Nov 6, 2026
262db4e
fix: retain multiline compound-literal cast warnings
DanceoftheAurora Nov 6, 2026
b9d2003
docs: describe multiline cast regression tests
DanceoftheAurora Nov 6, 2026
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1 change: 1 addition & 0 deletions CHANGELOG.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ Changelog
TBA
===

* Avoid casting warnings for unnamed parameters when a function body starts on the next line. (#131)
* Use path-aware prefix checks instead of deprecated os.path.commonprefix(). (#445)
* Fixed a whitespace/newline false positive for control conditions containing lambdas. (#410)
* We now error on relative include paths (``./``, ``../``). (#432)
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21 changes: 21 additions & 0 deletions cpplint.py
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Expand Up @@ -6802,6 +6802,27 @@ def CheckCStyleCast(filename, clean_lines, linenum, cast_type, pattern, error):
if re.match(r"^\s*(?:;|const\b|throw\b|final\b|override\b|[=>{),]|->)", remainder):
return False

# A function body can start on the next non-blank line. Require a return
# type and function name, or a lambda capture, so a compound literal's
# opening brace is not mistaken for a body.
signature_context = ReplaceAlternateTokens(line[: match.start(0)])
signature = re.search(r"(?:\b[\w:<>]+[\s*&]+(?:\w+::)*\w+|\])\s*$", signature_context)
if (
not remainder.strip()
and signature
and not re.search(
r"\b(?:return|throw|co_return|co_yield|co_await|delete|else|__extension__)\b",
signature.group(0),
)
and not re.search(r"\bdelete\s*\[\s*\]\s*$", signature_context)
):
for next_linenum in range(linenum + 1, clean_lines.NumLines()):
next_line = clean_lines.elided[next_linenum].strip()
if next_line:
if next_line.startswith("{"):
return False
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break

# At this point, all that should be left is actual casts.
error(
filename,
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59 changes: 59 additions & 0 deletions cpplint_unittest.py
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Expand Up @@ -1054,6 +1054,65 @@ def testCheckForUnnamedParams(self):
self.TestLint("void f(int /*unused*/) override {", "")
self.TestLint("void f(int /*unused*/) final {", "")

@pytest.mark.parametrize(
"signature",
[
"void Func(int)",
"void Func(int*)",
"const Foo* Func(int)",
"void ns::Func(int)",
"auto func = [](int)",
"auto func = [value](int)",
"return [](int)",
],
)
@pytest.mark.parametrize("separator", ["\n", "\n\n", "\n// Unused argument.\n"])
def testUnnamedParamBeforeMultilineBody(self, signature, separator):
"""Keep unnamed parameters before multiline function bodies free of cast warnings."""
code = signature + separator + "{\n return;\n}"
clean_lines = cpplint.CleansedLines(code.split("\n"))
error_collector = ErrorCollector(self.assertTrue)
cpplint.CheckCasts("foo.cc", clean_lines, 0, error_collector)
assert error_collector.Results() == ""

@pytest.mark.parametrize(
("code", "cast_type", "type_name"),
[
("int value = (int)\n 1.5;", "static_cast", "int"),
("return (int)\n (value);", "static_cast", "int"),
("int* ptr = (int*)\n value;", "reinterpret_cast", "int*"),
("int value = (int)\n// Cast operand.\n 1.5;", "static_cast", "int"),
("int value = (int)\n", "static_cast", "int"),
("int value = (int)\n{1};", "static_cast", "int"),
("return (int)\n{1};", "static_cast", "int"),
("return(int)\n{1};", "static_cast", "int"),
("throw (int)\n{1};", "static_cast", "int"),
("else return (int)\n{1};", "static_cast", "int"),
("else throw (int)\n{1};", "static_cast", "int"),
("else delete (int*)\n{0};", "reinterpret_cast", "int*"),
("delete [] (int*)\n{0};", "reinterpret_cast", "int*"),
("return __extension__ (int)\n{1};", "static_cast", "int"),
("int* ptr = (int*)\n{0};", "reinterpret_cast", "int*"),
("int value = 1 bitand (int)\n{1};", "static_cast", "int"),
("int value = not (int)\n{1};", "static_cast", "int"),
(
"void Func(int)\n{\n int value = (int)\n {1};\n}",
"static_cast",
"int",
),
],
)
def testMultilineCStyleCast(self, code, cast_type, type_name):
"""Retain diagnostics for multiline casts, compound literals, and incomplete casts."""
clean_lines = cpplint.CleansedLines(code.split("\n"))
error_collector = ErrorCollector(self.assertTrue)
for linenum in range(clean_lines.NumLines()):
cpplint.CheckCasts("foo.cc", clean_lines, linenum, error_collector)
assert error_collector.Results() == (
f"Using C-style cast. Use {cast_type}<{type_name}>(...) instead"
" [readability/casting] [4]"
)

# Test deprecated casts such as int(d)
def testDeprecatedCast(self):
self.TestLint(
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