https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64965
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> --- Andrew, if you write PR 66317 or Bug 66317 (or variations like Bug preprocessor/66317) then Bugzilla automatically makes it a hyperlink :-) Reproducer from that bug: Test case (a 2 line source file named "filename_bug.c"): #line 1 "new\nline.c" const char filename[] = __FILE__; Output of "cpp filename_bug.c" (there is no newline on the last line of output): # 1 "filename_bug.c" # 1 "<built-in>" # 1 "<command-line>" # 1 "/usr/include/stdc-predef.h" 1 3 4 # 1 "<command-line>" 2 # 1 "filename_bug.c" # 1 "new line.c" new line.c:1:1: warning: missing terminating " character new line.c:1:25: internal compiler error: invalid built-in macro "__FILE__" ... Also https://bugs.debian.org/838874