On 10/13/2021 10:06 AM, Björn 'besser82' Esser wrote:
Building with lto disabled is a bad idea, as Fedora intentionally
enabled lto by default.
Yes, but there is nothing inherently wrong with not using LTO. Many
packages opt-out for various reasons.
What you describe as lto requires a lot of memory is caused by building
lto along with non-lto in the same object file requires significantly
more memory. For that reason one can disable building non-lto along
with lto using the `-f-no-fat-lto-objects` compiler flags instead of
`-f-fat-lto-objects`, if and *only IF* the package in question does
*NOT* ship static libraries.
I doubt fat-lto-objects is the issue here. The "fat" stuff is ignored
at link time as the LTO bytecodes will take precedence. It is far more
likely that the parallel link with all those LTO bytecodes is what's
sucking up all the memory.
Note that we build with fat-lto-objects for a reason. If a package
installs any static objects, then those objects must be compiled down to
machine code as the LTO bytestreams are not compatible across GCC
releases. -ffat-lto-objects ensures this.
To remedy this situation you have to put in bits to
redhat-rpm-config/brp-whatever to fail builds when they install .o/.a
files into the buildroot that are purely LTO bytecode streams and
identify every package that fails that test and fix them to turn on
fat-lto-objects. I actually wrote some code to do this and ran a Fedora
build, but never had the time to act on the resultant data. I've since
left Red Hat and haven't had time to come back to the issue.
Jeff
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