[C2y] Handle FP-suffixes on prefixed octals (#141230)

[naveen-seth]

Fixes #141230.

Currently, prefixed octal literals used with floating-point suffixes are not
rejected, causing Clang to crash.
This adds proper handling to reject invalid literals such as 0o0.1 or 0.0e1.

No release note because this is fixing an issue with a new change.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Naveen Seth Hanig (naveen-seth)

Changes

Fixes #141230.

Prefixed octal literals crash in combination with floating-point suffixes instead of rejecting them.
This adds proper handling to reject literals such as 0o0. or 0.0e1.

No release note because this is fixing an issue with a new change.

---

Full diff: https://github.com/llvm/llvm-project/pull/141695.diff

2 Files Affected:

• (modified) clang/lib/Lex/LiteralSupport.cpp (+16-4)
• (modified) clang/test/C/C2y/n3353.c (+22)

diff --git a/clang/lib/Lex/LiteralSupport.cpp b/clang/lib/Lex/LiteralSupport.cpp
index 75ad977d64b24..3b941fc4c48b8 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, IsSingleZero = false;
+  bool IsSingleZero = false;
   if ((c1 == 'O' || c1 == 'o') && (s[1] >= '0' && s[1] <= '7')) {
     unsigned DiagId;
     if (LangOpts.C2y)
@@ -1432,14 +1432,26 @@ void NumericLiteralParser::ParseNumberStartingWithZero(SourceLocation TokLoc) {
     Diags.Report(TokLoc, DiagId);
     ++s;
     DigitsBegin = s;
-    SawOctalPrefix = true;
+    radix = 8;
+    s = SkipOctalDigits(s);
+    if (s == ThisTokEnd) {
+      // Done
+    } else if ((isHexDigit(*s) && *s != 'e' && *s != 'E' && *s != '.') &&
+               !isValidUDSuffix(LangOpts, StringRef(s, ThisTokEnd - s))) {
+      Diags.Report(Lexer::AdvanceToTokenCharacter(TokLoc, s - ThisTokBegin, SM,
+                                                  LangOpts),
+                   diag::err_invalid_digit)
+          << StringRef(s, 1) << 1;
+      hadError = true;
+    }
+    // Other suffixes will be diagnosed by the caller.
+    return;
   }
 
   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 &&
-        !IsSingleZero)
+    if (radix == 8 && LangOpts.C2y && !hadError && !IsSingleZero)
       Diags.Report(TokLoc, diag::warn_unprefixed_octal_deprecated);
   });
 
diff --git a/clang/test/C/C2y/n3353.c b/clang/test/C/C2y/n3353.c
index a616228f1bad0..d7d8b03501260 100644
--- a/clang/test/C/C2y/n3353.c
+++ b/clang/test/C/C2y/n3353.c
@@ -92,6 +92,28 @@ 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.
+auto f1 = 0o0.;  /* expected-error {{invalid suffix '.' on integer constant}}
+                    compat-warning {{octal integer literals are incompatible with standards before C2y}}
+                    ext-warning {{octal integer literals are a C2y extension}}
+                    cpp-warning {{octal integer literals are a Clang extension}}
+                */
+auto f2 = 0o0.1; /* expected-error {{invalid suffix '.1' on integer constant}}
+                    compat-warning {{octal integer literals are incompatible with standards before C2y}}
+                    ext-warning {{octal integer literals are a C2y extension}}
+                    cpp-warning {{octal integer literals are a Clang extension}}
+                */
+auto f3 = 0o0e1; /* expected-error {{invalid suffix 'e1' on integer constant}}
+                    compat-warning {{octal integer literals are incompatible with standards before C2y}}
+                    ext-warning {{octal integer literals are a C2y extension}}
+                    cpp-warning {{octal integer literals are a Clang extension}}
+                 */
+auto f4 = 0o0E1; /* expected-error {{invalid suffix 'E1' on integer constant}}
+                    compat-warning {{octal integer literals are incompatible with standards before C2y}}
+                    ext-warning {{octal integer literals are a C2y extension}}
+                    cpp-warning {{octal integer literals are a Clang extension}}
+                 */
+
 // Ensure digit separators work as expected.
 constexpr int p = 0o0'1'2'3'4'5'6'7; /* compat-warning {{octal integer literals are incompatible with standards before C2y}}
                                         ext-warning {{octal integer literals are a C2y extension}}

[shafik]

Can you provide the PR that brought in the change you are fixing?

Looks like this is from: 9cf46fb

[naveen-seth]

Thank you for reviewing this so quickly! I was just about to tag @AaronBallman, since this PR fixes a bug that was introduced when octal prefixes were added in #131626.

[AaronBallman]

I added @cor3ntin and @tahonermann for some extra sets of eyes, seeing as how I already messed this up once before. :-)

[naveen-seth]

Ping

[AaronBallman]

LGTM!

[cor3ntin]

Please extract Lexer::AdvanceToTokenCharacter(TokLoc, s - ThisTokBegin, SM, LangOpts) in a variable

[cor3ntin]

Do we have tests showing 00. , 01. 0E1 etc do not produce extension warnings?

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[naveen-seth]

Thanks for the review.
In case the changes get approved, please also merge it on my behalf since I don't have commit access yet. Thank you!