https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116730
--- Comment #19 from Jonathan Wakely <redi at gcc dot gnu.org> --- Right, you seem repeatedly confused about the difference between the build dir and the source dir. The libbacktrace/*.c files are in the source dir. The paths to those is fixed relative to the libstdc++-v3/src/libbacktrace dir in the source tree, it doesn't change depending on your build. So comment 13 ("it looks like the build files were originally being made with hard-coded paths specific to the build setup of the dev in question") is nonsense. The paths like ../../../libbacktrace/atomic.c are the relative path from one source dir to another source dir, which is fixed.