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The current implementation checks repeatedly if `tc-is-lto` is true. In addition to running a small compile check redundantly, this has a potential correctness downside. An ebuild could do this: ``` lto-guarantee-fat tc-is-lto && myeconfargs+=( --enable-lto ) filter-lto ``` The idea is, the configure script has special handling and simply adding -flto is too "simple" to work. e.g. not all sources build with LTO. When this happens, strip-lto-bytecode "thinks" we didn't build with LTO at all, and returns early. By tracking state across functions -- and across phases -- we can reliably tell if `lto-guarantee-fat` actually "succeeded". Bug: https://bugs.gentoo.org/958412 Acked-by: Sam James <sam@gentoo.org> Signed-off-by: Eli Schwartz <eschwartz@gentoo.org>
128 lines
3.4 KiB
Bash
128 lines
3.4 KiB
Bash
# Copyright 2025 Gentoo Authors
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# Distributed under the terms of the GNU General Public License v2
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# @ECLASS: dot-a.eclass
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# @MAINTAINER:
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# Toolchain Ninjas <toolchain@gentoo.org>
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# @AUTHOR:
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# Sam James <sam@gentoo.org>
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# Eli Schwartz <eschwartz@gentoo.org>
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# @SUPPORTED_EAPIS: 8
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# @BLURB: Functions to handle stripping LTO bytecode out of static archives.
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# @DESCRIPTION:
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# This eclass provides functions to strip LTO bytecode out of static archives
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# (.a files).
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#
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# Static libraries when built with LTO will contain LTO bytecode which is
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# not portable across compiler versions or compiler vendors. To avoid pessimising
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# the library and always filtering LTO, we can build it with -ffat-lto-objects
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# instead, which builds some components twice. The installed part will then
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# have the LTO contents stripped out, leaving the regular objects in the
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# static archive.
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#
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# Use should be passing calling lto-guarantee-fat before configure-time
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# and calling strip-lto-bytecode after installation.
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#
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# Most packages installing static libraries should be using this eclass,
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# though it's not strictly necessary if the package filters LTO.
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#
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# @EXAMPLE:
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# @CODE
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#
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# inherit dot-a
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#
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# src_configure() {
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# lto-guarantee-fat
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# econf
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# }
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#
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# src_install() {
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# default
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# strip-lto-bytecode
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# }
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case ${EAPI} in
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8) ;;
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*) die "${ECLASS}: EAPI ${EAPI:-0} not supported" ;;
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esac
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if [[ -z ${_DOT_A_ECLASS} ]] ; then
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_DOT_A_ECLASS=1
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inherit flag-o-matic toolchain-funcs
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# @VARIABLE: _DOT_A_IS_LTO
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# @INTERNAL
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# @DESCRIPTION:
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# Records the state of tc-is-lto across eclass function calls.
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_DOT_A_IS_LTO=0
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# TODO: QA check
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# @FUNCTION: lto-guarantee-fat
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# @DESCRIPTION:
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# If LTO is enabled, appends -ffat-lto-objects or any other flags needed
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# to provide fat LTO objects.
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lto-guarantee-fat() {
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tc-is-lto || return
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_DOT_A_IS_LTO=1
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# We add this for all languages as LTO obviously can't be done
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# if different compilers are used for e.g. C vs C++ anyway.
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append-flags $(test-flags-CC -ffat-lto-objects)
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}
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# @FUNCTION: strip-lto-bytecode
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# @USAGE: [library|directory] [...]
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# @DESCRIPTION:
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# Strips LTO bytecode from libraries (static archives) passed as arguments.
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# Defaults to operating on ${ED} as a whole if no arguments are passed.
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#
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# As an optimisation, if USE=static-libs exists for a package and is disabled,
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# the default-searching behaviour with no arguments is suppressed.
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strip-lto-bytecode() {
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if [[ ${_DOT_A_IS_LTO} != 1 ]] && ! tc-is-lto; then
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return
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fi
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local files=()
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if [[ ${#} -eq 0 ]]; then
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if ! in_iuse static-libs || use static-libs ; then
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# maybe we are USE=static-libs. Alternatively, maybe the ebuild doesn't
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# offer such a choice. In both cases, the user specified the function,
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# so we expect to be called on *something*, but nothing was explicitly
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# passed. Try scanning ${ED} automatically.
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set -- "${ED}"
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else
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return
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fi
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fi
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mapfile -t -d '' files < <(find -H "${@}" -type f \( -name '*.a' -or -name '*.o' \) -print0)
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local toolchain_type=
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tc-is-gcc && toolchain_type=gnu
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tc-is-clang && toolchain_type=llvm
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local file
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for file in "${files[@]}" ; do
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case ${toolchain_type} in
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gnu)
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$(tc-getSTRIP) \
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-R .gnu.lto_* \
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-R .gnu.debuglto_* \
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-N __gnu_lto_v1 \
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"${file}" || die "Stripping bytecode in ${file} failed"
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;;
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llvm)
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llvm-bitcode-strip \
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-r "${file}" \
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-o "${file}" || die "Stripping bytecode in ${file} failed"
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;;
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*)
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;;
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esac
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done
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}
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fi
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