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We need a libgcc to build glibc. Tranditionally we therefore build a non-threaded and non-shared compiler (gcc-cross-initial), then use that to build libgcc-initial which is used to build glibc which we can then build gcc-cross and libgcc against. Firstly, we can drop the glibc dependency from gcc-cross, *if* we make two changes: a) specify the minimum glibc version to support in a configure option b) create a dummy limits.h file so that later when glibc creates one, the headers structure has support for it. We can do this with a simple empty file Once gcc-cross is libc independent, we can use it to build both libgcc-initial and then later libgcc. libgcc-initial is tricky as we need to imitate the non-threaded and non-shared case. We can do that by hacking the threading mode back to "single" even if gcc reports "posix" and disable libc presence for the libgcc-intial build. We have to create the dummy limits.h to avoid compiler errors from a missing header. glibc will fail to link with libgcc-initial due to a missing "exception handler" capable libgcc (libgcc_eh.a). Since we know glibc doesn't need any exception handler, we can safely symlink to libgcc.a. With those changes, gcc-cross can be used in all places and we only need one build of gcc for each architecture. For some reason ifunc was being disabled on mips prior to these changes but afterwards became enabled but caused assertion failures. This is therefore disabled until we can debug that. (From OE-Core rev: 62b7308b8c4d2b439a15a4f7cbc6f823077bb0be) Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
QEMU Emulation Targets ====================== To simplify development, the build system supports building images to work with the QEMU emulator in system emulation mode. Several architectures are currently supported in 32 and 64 bit variants: * ARM (qemuarm + qemuarm64) * x86 (qemux86 + qemux86-64) * PowerPC (qemuppc only) * MIPS (qemumips + qemumips64) Use of the QEMU images is covered in the Yocto Project Reference Manual. The appropriate MACHINE variable value corresponding to the target is given in brackets.