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[C2y] Correctly handle 0 in the preprocessor #137844

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Merged
merged 2 commits into from
Apr 30, 2025
Merged

[C2y] Correctly handle 0 in the preprocessor #137844

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c79efa3
[C2y] Correctly handle 0 in the preprocessor
AaronBallman Apr 29, 2025
e217c3d
Update based on review feedback
AaronBallman Apr 29, 2025
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7 changes: 5 additions & 2 deletions clang/lib/Lex/LiteralSupport.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1420,7 +1420,7 @@ void NumericLiteralParser::ParseNumberStartingWithZero(SourceLocation TokLoc) {
}

// Parse a potential octal literal prefix.
bool SawOctalPrefix = false;
bool SawOctalPrefix = false, IsSingleZero = false;
if ((c1 == 'O' || c1 == 'o') && (s[1] >= '0' && s[1] <= '7')) {
unsigned DiagId;
if (LangOpts.C2y)
Expand All @@ -1438,7 +1438,8 @@ void NumericLiteralParser::ParseNumberStartingWithZero(SourceLocation TokLoc) {
auto _ = llvm::make_scope_exit([&] {
// If we still have an octal value but we did not see an octal prefix,
// diagnose as being an obsolescent feature starting in C2y.
if (radix == 8 && LangOpts.C2y && !SawOctalPrefix && !hadError)
if (radix == 8 && LangOpts.C2y && !SawOctalPrefix && !hadError &&
!IsSingleZero)
Diags.Report(TokLoc, diag::warn_unprefixed_octal_deprecated);
});

Expand All @@ -1453,6 +1454,8 @@ void NumericLiteralParser::ParseNumberStartingWithZero(SourceLocation TokLoc) {
// anything, we leave the digit start where it was.
if (s != PossibleNewDigitStart)
DigitsBegin = PossibleNewDigitStart;
else
IsSingleZero = (s == ThisTokEnd); // Is the only thing we've seen a 0?

if (s == ThisTokEnd)
return; // Done, simple octal number like 01234
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4 changes: 4 additions & 0 deletions clang/test/C/C2y/n3353.c
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Expand Up @@ -46,6 +46,10 @@ static const void *ptr = 0o0; /* ext-warning {{octal integer literals are a C2y
// 0 by itself is not deprecated, of course.
int k = 0;

// Test a preprocessor use of 0 by itself, which is also not deprecated.
#if 0
#endif

// Make sure there are no surprises with auto and type deduction. Promotion
// turns this into an 'int', and 'constexpr' implies 'const'.
constexpr auto l = 0o1234567; /* ext-warning {{octal integer literals are a C2y extension}}
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