bad error message on incorrect string literal #18079

[akshaykumars614]

(bad error message on incorrect string literal)

Fixed the error message for incorrect string literal

before:

test.cpp:1:19: error: invalid character '
' character in raw string delimiter; use PREFIX( )PREFIX to delimit raw string
char const* a = R"
                  ^

now:

test.cpp:1:19: error: invalid newline character in raw string delimiter; use PREFIX( )PREFIX to delimit raw string
    1 | char const* a = R"
      |                   ^

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[llvmbot]

@llvm/pr-subscribers-clang

Author: None (akshaykumars614)

Changes

(bad error message on incorrect string literal)

Fixed the error message for incorrect string literal

before:

test.cpp:1:19: error: invalid character '
' character in raw string delimiter; use PREFIX( )PREFIX to delimit raw string
char const* a = R"
^

now:

test.cpp:1:19: error: invalid newline character in raw string delimiter; use PREFIX( )PREFIX to delimit raw string
1 | char const* a = R"
| ^

---

Full diff: https://github.com/llvm/llvm-project/pull/81670.diff

1 Files Affected:

• (modified) clang/include/clang/Basic/DiagnosticLexKinds.td (+1-1)

diff --git a/clang/include/clang/Basic/DiagnosticLexKinds.td b/clang/include/clang/Basic/DiagnosticLexKinds.td
index 75ca2fa16d3485..c5a2096d02b39d 100644
--- a/clang/include/clang/Basic/DiagnosticLexKinds.td
+++ b/clang/include/clang/Basic/DiagnosticLexKinds.td
@@ -100,7 +100,7 @@ def err_raw_delim_too_long : Error<
   "raw string delimiter longer than 16 characters"
   "; use PREFIX( )PREFIX to delimit raw string">;
 def err_invalid_char_raw_delim : Error<
-  "invalid character '%0' character in raw string delimiter"
+  "invalid newline character in raw string delimiter"
   "; use PREFIX( )PREFIX to delimit raw string">;
 def err_unterminated_raw_string : Error<
   "raw string missing terminating delimiter )%0\"">;

[akshaykumars614]

I am new to this project. Please let me know if any files need to be added.

I don't believe any testing or test suite changes are required for this change.

[jroelofs]

I am new to this project. Please let me know if any files need to be added.

I don't believe any testing or test suite changes are required for this change.

This particular change will break this usage of that diagnostic, which expects that format argument:

llvm-project/clang/lib/Lex/Lexer.cpp

Lines 2274 to 2275 in e06f352

	Diag(PrefixEnd, diag::err_invalid_char_raw_delim)
	<< StringRef(PrefixEnd, 1);

The change needs to account for cases where the character should still be printed, and when it isn't printable or would have strange formatting. And then it should be accompanied by a test that verifies the new behavior.

[akshaykumars614]

Got it. Thank you for helping me. I will look upon it further. Now should I close this pull request or add the updated commit here itself?

[jroelofs]

Feel free to keep it open and push more commits to the branch.

[github-actions]

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

[jroelofs]

LGTM. Let me know if you need me to press the "merge" button for you.

[akshaykumars614]

Thank you for reviewing:)

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[ldrumm]

Should we be looking for \r as well?

If the testcase is checked out with DOS line endings (e.g. on a windows machine), then the test clang/test/Lexer/raw-string-dlim-invalid.cpp fails

I don't know what the C++ spec says, but I think this diagnostic should work for both common end of line styles.

Something like this:

diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index c98645993abe..e2ab928c04ee 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -2270,7 +2270,7 @@ bool Lexer::LexRawStringLiteral(Token &Result, const char *CurPtr,
       const char *PrefixEnd = &CurPtr[PrefixLen];
       if (PrefixLen == 16) {
         Diag(PrefixEnd, diag::err_raw_delim_too_long);
-      } else if (*PrefixEnd == '\n') {
+      } else if ((*PrefixEnd == '\r' && PrefixEnd[1] == '\n') || *PrefixEnd == '\n') {
         Diag(PrefixEnd, diag::err_invalid_newline_raw_delim);
       } else {
         Diag(PrefixEnd, diag::err_invalid_char_raw_delim)

?

[cor3ntin]

It would be better to do, in all cases

 Diag(PrefixEnd, diag::err_invalid_char_raw_delim) <<  escapeCStyle<EscapeChar::Single>(*PrefixEnd);

(and remove the err_invalid_newline_raw_delim diagnostic altogether)