https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108534
--- Comment #2 from Ian Lance Taylor <ian at airs dot com> --- Yes, it's a relative path, such as #line 1 "cgo-gcc-prolog" These are dummy but informative line markers used to separate generated code from user-written code, so that compiler error messages report problems in the right place. The compiler is being executed in a temporary directory created during the build, so the working directory is meaningless. Other references to files in that temporary directory are rewritten by a -fdebug-prefix-map option. Unfortunately, that option fails to rename the working directory that is pulled in for the relative #line option.