All the reasons of commit are described in a bug report in bugzilla there https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105005 .
results of edge case testing with adequate console output after "gcc -E example.c -o example" command: 1)
1 #line
2 #warning "some warning, not an EOF"
example.c:1:6: error: missing #line directive arguments
1 | #line
| ^
example.c:2:2: warning: #warning "some warning, not an EOF" [-Wcpp]
2 | #warning "some warning, not an EOF"
| ^~~~~~~
1 #line
2
example.c:1:6: error: missing #line directive arguments
1 | #line
| ^
1 #line
example.c:1:6: error: unexpected end of file after #line
1 | #line
| ^