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[clang-format]: Treat #pragma once as include guard for IndentPPDirectives #135443

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[clang-format]: Treat #pragma once as include guard for IndentPPDirectives #135443

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d4e3ae0
[clang-format]: Treat #pragma once as include guard for IndentPPDirec…
saltyJeff Apr 11, 2025
ccafba9
Merge branch 'main' into main
saltyJeff Apr 11, 2025
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11 changes: 9 additions & 2 deletions clang/lib/Format/UnwrappedLineParser.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1102,11 +1102,18 @@ void UnwrappedLineParser::parsePPIf(bool IfDef) {
conditionalCompilationStart(Unreachable);
FormatToken *IfCondition = FormatTok;
// If there's a #ifndef on the first line, and the only lines before it are
// comments, it could be an include guard.
// comments or #pragma once, it could be an include guard.
bool MaybeIncludeGuard = IfNDef;
if (IncludeGuard == IG_Inited && MaybeIncludeGuard) {
for (auto &Line : Lines) {
if (Line.Tokens.front().Tok->isNot(tok::comment)) {
bool LineIsComment = Line.Tokens.front().Tok->is(tok::comment);
auto TokenIterator = Line.Tokens.begin();
bool LineIsPragmaOnce = Line.Tokens.size() >= 3 &&
TokenIterator->Tok->is(tok::hash) &&
(++TokenIterator)->Tok->is(tok::pp_pragma) &&
(++TokenIterator)->Tok->TokenText == "once";

if (!LineIsComment && !LineIsPragmaOnce) {
MaybeIncludeGuard = false;
IncludeGuard = IG_Rejected;
break;
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12 changes: 11 additions & 1 deletion clang/unittests/Format/FormatTest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -6223,6 +6223,16 @@ TEST_F(FormatTest, IndentPreprocessorDirectives) {
"int z;\n"
"#endif",
Style);
// Treat #pragma once as part of an include guard.
verifyFormat("#pragma once\n"
"#ifndef HEADER_H\n"
"#define HEADER_H\n"
"#ifdef NOT_GUARD\n"
"# define NOT_GUARD\n"
"#endif\n"
"code();\n"
"#endif",
Style);
// FIXME: This doesn't handle the case where there's code between the
// #ifndef and #define but all other conditions hold. This is because when
// the #define line is parsed, UnwrappedLineParser::Lines doesn't hold the
Expand All @@ -6239,7 +6249,7 @@ TEST_F(FormatTest, IndentPreprocessorDirectives) {
"#endif",
Style);
// FIXME: This doesn't handle cases where legitimate preprocessor lines may
// be outside an include guard. Examples are #pragma once and
// be outside an include guard. Examples include
// #pragma GCC diagnostic, or anything else that does not change the meaning
// of the file if it's included multiple times.
verifyFormat("#ifdef WIN32\n"
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