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[clang] Don't warn on zero literals with -std=c2y #149688

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Jul 21, 2025
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[clang] Don't warn on zero literals with -std=c2y #149688

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5def3c2
[clang] Don't warn on zero literals with -std=c2y
anematode Jul 20, 2025
8fe76c6
Update clang/test/C/C2y/n3353.c
anematode Jul 20, 2025
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2 changes: 1 addition & 1 deletion clang/lib/Lex/LiteralSupport.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1467,7 +1467,7 @@ void NumericLiteralParser::ParseNumberStartingWithZero(SourceLocation TokLoc) {
if (s != PossibleNewDigitStart)
DigitsBegin = PossibleNewDigitStart;
else
IsSingleZero = (s == ThisTokEnd); // Is the only thing we've seen a 0?
IsSingleZero = (s == ThisTokBegin + 1);

if (s == ThisTokEnd)
return; // Done, simple octal number like 01234
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11 changes: 6 additions & 5 deletions clang/test/C/C2y/n3353.c
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Expand Up @@ -44,7 +44,12 @@ static const void *ptr = 0o0; /* ext-warning {{octal integer literals are a C2y
#endif

// 0 by itself is not deprecated, of course.
int k = 0;
int k1 = 0;
unsigned int k2 = 0u;
long k3 = 0l;
unsigned long k4 = 0ul;
long long k5 = 0ll;
unsigned long long k6 = 0ull;

// Test a preprocessor use of 0 by itself, which is also not deprecated.
#if 0
Expand All @@ -65,7 +70,6 @@ static_assert(__extension__ _Generic(typeof(l), const int : 1, default : 0)); //

// Note that 0o by itself is an invalid literal.
int m = 0o; /* expected-error {{invalid suffix 'o' on integer constant}}
c2y-warning {{octal literals without a '0o' prefix are deprecated}}
*/

// Ensure negation works as expected.
Expand All @@ -83,13 +87,11 @@ int n = 0o18; /* expected-error {{invalid digit '8' in octal constant}}
cpp-warning {{octal integer literals are a Clang extension}}
*/
int o1 = 0o8; /* expected-error {{invalid suffix 'o8' on integer constant}}
c2y-warning {{octal literals without a '0o' prefix are deprecated}}
*/
// FIXME: however, it matches the behavior for hex literals in terms of the
// error reported. Unfortunately, we then go on to think 0 is an octal literal
// without a prefix, which is again a bit confusing.
int o2 = 0xG; /* expected-error {{invalid suffix 'xG' on integer constant}}
c2y-warning {{octal literals without a '0o' prefix are deprecated}}
*/

// Show that floating-point suffixes on octal literals are rejected.
Expand Down Expand Up @@ -130,7 +132,6 @@ constexpr int p = 0o0'1'2'3'4'5'6'7; /* compat-warning {{octal integer literals
*/
static_assert(p == 01234567); // c2y-warning {{octal literals without a '0o' prefix are deprecated}}
int q = 0o'0'1; /* expected-error {{invalid suffix 'o'0'1' on integer constant}}
c2y-warning {{octal literals without a '0o' prefix are deprecated}}
*/

#define M 0o123
Expand Down