search

crosstool-ng / crosstool-ng

A versatile (cross-)toolchain generator.
Other
2.07k stars 653 forks source link

canadian cross: host cflags are used as build cflags in final host gcc install #1755

Open sfackler opened 2 years ago

sfackler commented 2 years ago

I'm trying to set up a canadian cross build: x86_64-linux -> x86_64-macos -> x86_64-linux. I'm using https://github.com/tpoechtrager/osxcross for the macos cross compiler, with little shims to forward <prefix>-gcc to <prefix>-clang since it seems like crosstool-ng can't be told to look for clang directly.

One interesting aspect of this setup is that the build compiler is gcc and the host compiler is clang. This appears to break the final gcc compiler stage, with all of CFLAGS, CFLAGS_FOR_BUILD, and CFLAGS_FOR_HOST appearing to use the host configuration. In particular, the -Qunused-arguments flag is passed, which is only set when crosstool detects that a compiler is clang. Since this isn't true for the build compiler, things break. I've attached the failing config.log for reference as well.

It also looks like the build process is only overriding CC and not CXX for this final gcc step - I'm not sure if that's intentional or not? With crosstools configured to build an older gcc that doesn't have any C++, it gets a bit further along but fails in the libiberty build for the same reason.

build.log.gz config.log .config.txt

sfackler commented 2 years ago

Looking at .build/HOST-x86_64-apple-darwin/x86_64-linux-gnu/state/cc_for_host/env.sh, CFLAGS_FOR_BUILD and CFLAGS_FOR_HOST are still set properly at the point the cc_for_host step starts:

declare -g -- CT_CFLAGS_FOR_BUILD="-O2 -g -I/tmp/crosstool-ng/.build/HOST-x86_64-apple-darwin/x86_64-linux-gnu/buildtools/include "
declare -g -- CT_CFLAGS_FOR_HOST="-O2 -g -pipe -I/tmp/crosstool-ng/.build/HOST-x86_64-apple-darwin/x86_64-linux-gnu/buildtools/complibs-host/include  -Qunused-arguments -fno-common"
sfackler commented 2 years ago

It looks like the problem is in do_gcc_backend - CFLAGS_FOR_BUILD is based off of cflags, which is set to CT_CFLAGS_FOR_HOST:

https://github.com/crosstool-ng/crosstool-ng/blob/3d706748b49f9fa5adda5553227ddf16a1b0d552/scripts/build/cc/gcc.sh#L1179 https://github.com/crosstool-ng/crosstool-ng/blob/3d706748b49f9fa5adda5553227ddf16a1b0d552/scripts/build/cc/gcc.sh#L841

cpackham commented 2 years ago

hmm probably goes back to the unification of the core passes. We may have lost some changes that were specific to the canadian scenario.

sfackler commented 2 years ago

I have a WIP commit that gets closer to fixing things. It ironically appears that GCC's build system also doesn't handle this properly (it doesn't propagate CXXFLAGS_FOR_BUILD down to the libcpp sub-make). I have a gcc patch in that commit but it doesn't seem to fix the libcpp sub-make for some reason: https://github.com/sfackler/crosstool-ng/commit/4cba68d6abed45f40fac512ce86c20825f0fc945