Skip to content

[C2y] Correctly handle 0 in the preprocessor #137844

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 2 commits into from
Apr 30, 2025
Merged

[C2y] Correctly handle 0 in the preprocessor #137844

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
c79efa3
[C2y] Correctly handle 0 in the preprocessor
AaronBallman Apr 29, 2025
e217c3d
Update based on review feedback
AaronBallman Apr 29, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 5 additions & 2 deletions clang/lib/Lex/LiteralSupport.cpp
View file
Open in desktop
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, IsNakedZero = 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 &&
!IsNakedZero)
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
IsNakedZero = s == ThisTokEnd; // Is the only thing we've seen a 0?

if (s == ThisTokEnd)
return; // Done, simple octal number like 01234
Expand Down
4 changes: 4 additions & 0 deletions clang/test/C/C2y/n3353.c
View file
Open in desktop
Original file line number Diff line number Diff line change
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}}
Expand Down
Loading