Every now and then I notice a diagnostic where only a single character of a token (identifier?) is underlined but up until now I haven't had luck reproducing it (often times it involves macros).  The ill-formed C++ test case below shows one situation when this happens without macros.  Note the underlining in the second error.

$ cat t.C && gcc -S  -Wall t.C
int i = sizeof ((int));
t.C:1:18: error: expected primary-expression before ‘int’
    1 | int i = sizeof ((int));
      |                  ^~~
t.C:1:18: error: expected ‘)’ before ‘int’
    1 | int i = sizeof ((int));
      |                 ~^~~
      |                  )
t.C:1:23: error: expected ‘)’ before ‘;’ token
    1 | int i = sizeof ((int));
      |                ~      ^
      |                       )

Other C++ compilers as well as GCC's C front end handle this more gracefully.  They print just a single message along the lines of:

t.C:1:22: error: expected expression before ‘)’ token