https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118599
Bug ID: 118599 Summary: Incorrect diagnostic on multiline string literal Product: gcc Version: 15.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: egor.pugin at gmail dot com Target Milestone: --- https://godbolt.org/z/8oTdbx4bf Consider the following: #include <iostream> int main() { std::cerr << "1st line\m" "2nd line\n"; } gcc incorrectly gives: <source>: In function 'int main()': <source>:5:18: warning: unknown escape sequence: '\m' 5 | "2nd line\n"; | ^~~~~~~~~~~~ clang correctly gives: <source>:4:27: warning: unknown escape sequence '\m' [-Wunknown-escape-sequence] 4 | std::cerr << "1st line\m" | ^~