https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101473
--- Comment #19 from Richard Biener <rguenth at gcc dot gnu.org> --- I think it is a bug - -fdebug-prefix-map should be fully reflected in the LTO IL and thus we should not end up creating un-remapped references to files (we should not create many references to files late anyway). In particular we're remapping all files when streaming locations to LTO. But yes, we're explicitely _not_ streaming the -f*-prefix-map arguments since we'd have a hard time using them when they do not agree between TUs. Your lto-test shows the difference is in the LTRANS DWARF CU header: @@ -215,7 +215,7 @@ <9b> DW_AT_producer : (indirect string, offset: 0x1c7): GNU GIMPLE 10.3.0 -mtune=generic -march=x86-64 -g -O2 -fno-openmp -fno-openacc -fno-pie -fcf-protection=none -ffat-lto-objects -fuse-linker-plugin -fltrans <9f> DW_AT_language : 12 (ANSI C99) <a0> DW_AT_name : (indirect string, offset: 0x1b2): <artificial> - <a4> DW_AT_comp_dir : (indirect string, offset: 0x263): /tmp/lto-test/src0 + <a4> DW_AT_comp_dir : (indirect string, offset: 0x263): /tmp/lto-test/src1 <a8> DW_AT_ranges : 0x40 <ac> DW_AT_low_pc : 0x0 <b4> DW_AT_stmt_list : 0xe8 and with DWARF5 in addition in the directory table: The Directory Table (offset 0x10a, lines 1, columns 1): Entry Name - 0 (indirect line string, offset: 0xd): /tmp/lto-test/src0 + 0 (indirect line string, offset: 0xd): /tmp/lto-test/src1 so indeed the prefix remapping is needed at link-time - the link time CWD aka DW_AT_comp_dir might also not agree with the CWD at compile time. Thus my suggestion would be to indeed add -f*-prefix-map to LDFLAGS, at least I can't think of a good solution to the above issue. Eventually picking a random TU and copying the CWD from its compile-time to the link-time CUs would work. Or somehow not specifying a compilation-dir at all for those CUs?