*FLAGS-=-flto* in /etc/portage/package.cflags causes emerge --info not to output LDFLAGS

[blackteahamburger]

/etc/portage/make.conf:

source /etc/portage/make.conf.lto.defines

CFLAGS="-march=native -Ofast ${GRAPHITE} ${DEVIRTLTO} ${IPAPTA} ${SEMINTERPOS} ${FLTO} -fuse-linker-plugin -pipe"
CXXFLAGS="${CFLAGS}"
LDFLAGS="${LDFLAGS} -fuse-ld=mold"
...

/etc/portage/make.conf.lto.defines:

FLTO="-flto=${NTHREADS}"
GRAPHITE="-fgraphite-identity -floop-nest-optimize"
IPAPTA="-fipa-pta"
SEMINTERPOS="-fno-semantic-interposition"
DEVIRTLTO="-fdevirtualize-at-ltrans"

/etc/portage/package.cflags/plasma-systemmonitor.conf:

kde-plasma/plasma-systemmonitor *FLAGS-=-flto*

After emerging kde-plasma/plasma-systemmonitor with above:

emerge --info kde-plasma/plasma-systemmonitor:

kde-plasma/plasma-systemmonitor-5.27.10::gentoo was built with the following:
USE="-debug"
CFLAGS="-march=native -Ofast -fgraphite-identity -floop-nest-optimize -fdevirtualize-at-ltrans -fipa-pta -fno-semantic-interposition -fuse-linker-plugin -pipe -Wl,-O1 -Wl,--as-needed -fuse-ld=mold"
CXXFLAGS="-march=native -Ofast -fgraphite-identity -floop-nest-optimize -fdevirtualize-at-ltrans -fipa-pta -fno-semantic-interposition -fuse-linker-plugin -pipe -Wl,-O1 -Wl,--as-needed -fuse-ld=mold"

LDFLAGS is not output. However, without /etc/portage/package.cflags/plasma-systemmonitor.conf, emerge --info kde-plasma/plasma-systemmonitor:

kde-plasma/plasma-systemmonitor-5.27.10::gentoo was built with the following:
USE="-debug"
CFLAGS="-march=native -Ofast -fgraphite-identity -floop-nest-optimize -fdevirtualize-at-ltrans -fipa-pta -fno-semantic-interposition -flto=auto -fuse-linker-plugin -pipe -Wl,-O1 -Wl,--as-needed -fuse-ld=mold"
CXXFLAGS="-march=native -Ofast -fgraphite-identity -floop-nest-optimize -fdevirtualize-at-ltrans -fipa-pta -fno-semantic-interposition -flto=auto -fuse-linker-plugin -pipe -Wl,-O1 -Wl,--as-needed -fuse-ld=mold"
LDFLAGS="-Wl,-O1 -Wl,--as-needed -fuse-ld=mold -march=native -Ofast -fgraphite-identity -floop-nest-optimize -fdevirtualize-at-ltrans -fipa-pta -fno-semantic-interposition -flto=auto -fuse-linker-plugin -pipe"

Is this irrelevant or a bug?

[vaeth]

If LDFLAGS is not output it means that it is empty.

However, IIUC it should contain -fuse-ld=mold, and when I retry your above setting this is the case (and LDFLAGS is output). So I cannot reproduce the problem: I guess you must have some setting which remove the -fuse-ld=mold from LDFLAGS.

Note that without flto related flags, the C{,XX}FLAGS are by default not copied to LDFLAGS so that it is not surprising that LDFLAGS contains much more data without *FLAGS-=-flto*. But what is surprising is that the -fuse-ld=mold vanishes from LDFLAGS when you have explicitly set it and do not filter it anywhere.

[blackteahamburger]

However, IIUC it should contain -fuse-ld=mold, and when I retry your above setting this is the case (and LDFLAGS is output). So I cannot reproduce the problem: I guess you must have some setting which remove the -fuse-ld=mold from LDFLAGS.

I'm sure I don't have any settings to remove -fuse-ld=mold.

[vaeth]

Since I cannot reproduce it, I can only give some hints which might help to debug it:

You can try to add some debugging code to the code where the setting is removed, e.g. by putting

BashrcdEcho "some identifier $LDFLAGS"

in various places in the file 10-flag.sh. For instance at the beginning of FlagSetFlags - at this place the variable should have been taken unchanged - and at the beginning and end of FlagParseLine to understand which command perhaps removes it.