https://github.com/AaronBallman created
https://github.com/llvm/llvm-project/pull/137844
We do not diagnose 0 as a deprecated octal literal outside of the preprocessor.
This fixes a bug where we were accidentally diagnosing 0 from a preprocessor
conditional, however.
No release note because this is fixing an issue with a new change.
>From c79efa30ca5d014ca3dc267be4efd161e5d42527 Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aa...@aaronballman.com>
Date: Tue, 29 Apr 2025 12:42:49 -0400
Subject: [PATCH] [C2y] Correctly handle 0 in the preprocessor
We do not diagnose 0 as a deprecated octal literal outside of the
preprocessor. This fixes a bug where we were accidentally diagosing 0
from a preprocessor conditional, however.
No release note because this is fixing an issue with a new change.
---
clang/lib/Lex/LiteralSupport.cpp | 7 +++++--
clang/test/C/C2y/n3353.c | 4 ++++
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/clang/lib/Lex/LiteralSupport.cpp b/clang/lib/Lex/LiteralSupport.cpp
index 20933cc8dee69..340b6539afc7c 100644
--- a/clang/lib/Lex/LiteralSupport.cpp
+++ b/clang/lib/Lex/LiteralSupport.cpp
@@ -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)
@@ -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);
});
@@ -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
diff --git a/clang/test/C/C2y/n3353.c b/clang/test/C/C2y/n3353.c
index fb7f9439ac21b..a616228f1bad0 100644
--- a/clang/test/C/C2y/n3353.c
+++ b/clang/test/C/C2y/n3353.c
@@ -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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