Per-target toolchains don't work?

[nwf]

Xmake Version

v3.0.1+v301.3350cc5ab

Operating System Version and Architecture

Debian 13 powerpc64le

Describe Bug

xmake v3.0.1 does not honor per-target toolchains settings, despite the documentation strongly suggesting that this should work.

Expected Behavior

If a target()'s description invokes set_toolchains(), that should be reflected in the build (and link, and prepare?) commands used for that target, and such settings should not change the toolchains used by any other targets.

Project Configuration

toolchain("tc20")
	set_kind("standalone")
	set_toolset("cxx", "clang++")
	on_load(function (toolchain) toolchain:add("cxflags", "-std=c++20", {force = true}) end)
toolchain_end()

toolchain("tc23")
	set_kind("standalone")
	set_toolset("cxx", "clang++")
	on_load(function (toolchain) toolchain:add("cxflags", "-std=c++23", {force = true}) end)
toolchain_end()

target("a20")
	set_kind("static")
	set_toolchains("tc20")
	add_files("a.cc")
	after_load(function (target) print("--->", target:name(), target:get("toolchains")) end)
target_end()

target("a23")
	set_kind("static")
	set_toolchains("tc23")
	add_files("a.cc")
	after_load(function (target) print("--->", target:name(), target:get("toolchains")) end)
target_end()

Additional Information and Error Logs

We can see that at least some part of xmake thinks it's doing the right thing, as the two targets' after_load callbacks print out the right toolchain names:

---> a20 tc20
---> a23 tc23

But when building (xmake -v), we see that everything in sight gets built with -std=c++20, as if tc20 were the only toolchain defined:

[ 23%]: cache compiling.release a.cc
/usr/bin/clang++ -c -Qunused-arguments -std=c++20 -o build/.objs/a20/linux/ppc64/release/a.cc.o a.cc
[ 35%]: linking.release liba20.a
/usr/bin/ar -cr build/linux/ppc64/release/liba20.a build/.objs/a20/linux/ppc64/release/a.cc.o
[ 59%]: cache compiling.release a.cc
/usr/bin/clang++ -c -Qunused-arguments -std=c++20 -o build/.objs/a23/linux/ppc64/release/a.cc.o a.cc
[ 71%]: linking.release liba23.a
/usr/bin/ar -cr build/linux/ppc64/release/liba23.a build/.objs/a23/linux/ppc64/release/a.cc.o
[100%]: build ok, spent 0.614s

[waruqi]

I know the reason, but I need some time to fix it. I haven't had much free time lately.

[nwf]

It's less urgent than I originally thought; we now just use the one toolchain() and have some target()s override the relevant flags.

[waruqi]

try this patch again. #6686

[waruqi]

Does it work now?

[nwf]

Yes, seems to:

---> a20 tc20
---> a23 tc23
[ 23%]: cache compiling.release a.cc
/usr/bin/clang++ -c -Qunused-arguments -std=c++20 -o build/.objs/a20/linux/ppc64/release/a.cc.o a.cc
[ 35%]: linking.release liba20.a
/usr/bin/ar -cr build/linux/ppc64/release/liba20.a build/.objs/a20/linux/ppc64/release/a.cc.o
[ 59%]: cache compiling.release a.cc
/usr/bin/clang++ -c -Qunused-arguments -std=c++23 -o build/.objs/a23/linux/ppc64/release/a.cc.o a.cc
[ 71%]: linking.release liba23.a
/usr/bin/ar -cr build/linux/ppc64/release/liba23.a build/.objs/a23/linux/ppc64/release/a.cc.o
[100%]: build ok, spent 0.719s

Thanks a lot!