Thomas Petazzoni 6063a8fbcf toolchain: switch to a two stage gcc build ... Currently, the internal toolchain backend does a three stage gcc build, with the following sequence of builds: - build gcc-initial - configure libc, install headers and start files - build gcc-intermediate - build libc - build gcc-final However, it turns out that this is not necessary, and only a two stage gcc build is needed. At some point, it was believed that a three stage gcc build was needed for NPTL based toolchains with old gcc versions, but even a gcc 4.4 build with a NPTL toolchain works fine. So, this commit switches the internal toolchain backend to use a two stage gcc build: just gcc-initial and gcc-final. It does so by: * Removing the custom dependency of all C libraries build step to host-gcc-intermediate. Now the C library packages simply have to depend on host-gcc-initial as a normal dependency (which they already do), and that's it. * Build and install both gcc *and* libgcc in host-gcc-initial. Previously, only gcc was built and installed in host-gcc-initial. libgcc was only done in host-gcc-intermediate, but now we need libgcc to build the C library. * Pass appropriate environment variables to get SSP (Stack Smashing Protection) to work properly: - Tell the compiler that the libc will provide the SSP support, by passing gcc_cv_libc_provides_ssp=yes. In Buildroot, we have chosen to use the SSP support from the C library instead of the SSP support from the compiler (this is not changed by this patch series, it was already the case). - Tell glibc to *not* build its own programs with SSP support. The issue is that if glibc detects that the compiler supports -fstack-protector, then glibc uses it to build a few things with SSP. However, at this point, the support is not complete (we only have host-gcc-initial, and the C library is not completely built). So, we pass libc_cv_ssp=no to tell the C library to not use SSP support itself. Note that this is not a big loss: only a few parts of the C library were built with -fstack-protector, not the entire library. * A special change is needed for ARC, because its libgcc depends on the C library, which breaks building libgcc in host-gcc-initial. This looks like a bug in the ARC compiler, as it does not obey the inhibit_libc variable which tells the compiler build process to *not* enable things that depend on the C library. So for now, in host-gcc-initial, we simply disable the build of libgmon.a for ARC. It's going to be built as part of host-gcc-final, so the final compiler will have gmon support. Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>		2014-09-14 23:20:23 +02:00
..
gcc-initial.mk	toolchain: switch to a two stage gcc build	2014-09-14 23:20:23 +02:00