...gcc/cp/mangle.c mentions DEBUG_MANGLE. Since I'm trying to figure out how gcc 4.2.3 is mangling thunk names, I thought I'd build gcc 4.2.3 with that macro turned on: make BOOT_CFLAGS="-DDEBUG_MANGLE" bootstrap ...but this does not succeed; the build fails with an internal compiler error caused by a segmentation fault. Does anyone have any experience building a relatively recent gcc with DEBUG_MANGLE turned on?