[Bug c/86721] New: use of undeclared identifier

[zhonghao at pku dot org.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86721

            Bug ID: 86721
           Summary: use of undeclared identifier
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhonghao at pku dot org.cn
  Target Milestone: ---

The code is as follow:

void g() {
 __builtin_printf(
 u8R"abcd(%.)abcd"
 "*d");
}

gcc accepts it, but clang rejects it:

code1.c:3:2: error: use of undeclared identifier 'u8R'
     u8R"abcd(%.)abcd"
     ^
    1 error generated.

This diagnostic seems to be right?