"R. Diez" <rdiezmail-gcc@xxxxxxxx> writes: > I am trying to enable C++ exception handling with the new --eh-frame-hdr method on my GCC 4.5.3 + newlib cross-compiler for an embedded PowerPC EABI target. > > I found this logic in file gcc/unwind-dw2-fde-glibc.c : > > #if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \ > && (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ > 2) \ > || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && defined(DT_CONFIG))) > # define USE_PT_GNU_EH_FRAME > #endif > > #if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR) \ > && defined(__FreeBSD__) && __FreeBSD__ >= 7 > # define ElfW __ElfN > # define USE_PT_GNU_EH_FRAME > #endif > > I guess that means the --eh-frame-hdr method will only work for glibc and FreeBSD, and nothing else. > > However, I would like to use --eh-frame-hdr in my embedded application too, which uses a small realtime OS and newlib. I thought support for --eh-frame-hdr depended on the linker, and not on the libc or the operating system. Or am I missing something? > > If that's the case, I guess I could patch that file to always define USE_PT_GNU_EH_FRAME. Or is there anything else I should be aware of? I wonder if GCC needs a new ./configure switch like "--enable-eh-frame-hdr-support", as hard-coding this logic does not seem like a good idea, given the great number of operating systems and libraries out there. The --eh-frame-hdr option will work provided you have a way to locate the exception frame header at runtime. The --eh-frame-hdr option creates a new PT_GNU_EH_FRAME program segment. At runtime the library will call dl_iterate_phdr to find that segment (in _Unwind_Find_FDE in unwind-dw2-fde-glibc.c). Your realtime OS probably does not provide dl_iterate_phdr, and you probably don't load the program segments onto the embedded system anyhow. So you can use something very similar to --eh-frame-hdr, but you will probably have to invent some new way to locate the information at runtime. And when you do that you will have to change crtstuff.c and some unwind-dw2-XX.c file as well. Ian
