phosek added inline comments.
================
Comment at: libcxx/cmake/Modules/HandleLibCXXABI.cmake:66
install(FILES "${LIBCXX_BINARY_INCLUDE_DIR}/${fpath}"
- DESTINATION ${LIBCXX_INSTALL_HEADER_PREFIX}include/c++/v1/${dstdir}
+ DESTINATION
${LIBCXX_INSTALL_HEADER_PREFIX}${CMAKE_INSTALL_INCLUDEDIR}/c++/v1/${dstdir}
COMPONENT cxx-headers
----------------
ldionne wrote:
> Ericson2314 wrote:
> > ldionne wrote:
> > > compnerd wrote:
> > > > Ericson2314 wrote:
> > > > > compnerd wrote:
> > > > > > @ldionne - how is the `LIBCXX_INSTALL_HEADER_PREFIX` used? Can
> > > > > > altering the value of `CMAKE_INSTALL_INCLUDEDIR` serve the purpose?
> > > > > It is sometimes modified to be per target when multiple targets are
> > > > > being used at once. All things `CMAKE_INSTALL_*` are globally scoped
> > > > > so in general the combination builds are quite awkward.
> > > > >
> > > > > (Having worked on Meson, I am really missing
> > > > > https://mesonbuild.com/Subprojects.html which is exactly what's
> > > > > needed to do this without these bespoke idioms that never work well
> > > > > enough . Alas...)
> > > > I don't think that bringing up other build systems is particularly
> > > > helpful.
> > > >
> > > > I do expect it to be modified, and I suspect that this is used
> > > > specifically for builds that @ldionne supports.
> > > Actually, I've never used it myself, but @phosek seems to be using it for
> > > the Runtimes build to output one set of headers for each target, as
> > > mentioned above.
> > >
> > > It seems to me that tweaking `CMAKE_INSTALL_PREFIX` globally when driving
> > > the libc++ build from the runtimes build would be more in-line with the
> > > CMake way of doing things (one configuration == one build), but I'm
> > > curious to hear what @phosek has to say about that.
> > > It seems to me that tweaking CMAKE_INSTALL_PREFIX globally when driving
> > > the libc++ build from the runtimes build would be more in-line with the
> > > CMake way of doing things (one configuration == one buid)
> >
> > You mean trying to mutate it during the libc++ CMake eval and then set it
> > back after? That would keep the intended meaning of `CMAKE_INSTALL_PREFIX`
> > being the actual prefix, but that feels awfully fragile to me. Or do you
> > mean something else?
> I keep forgetting that the runtimes build uses `add_subdirectory` to include
> each sub-project instead of driving a proper CMake build for each of those.
>
> Basically, what I'm saying is that whatever place we decide to build for N
> multiple targets, we should perform N different CMake builds setting the
> appropriate `CMAKE_INSTALL_PREFIX`, one for each target. But that discussion
> should happen elsewhere, not on this review.
>
> As far as this review is concerned, I do believe you want instead:
>
> ```
> ${CMAKE_INSTALL_INCLUDEDIR}${LIBCXX_INSTALL_HEADER_PREFIX}
> ```
>
> (reversed the order of variables)
>
> We should have @phosek confirm.
@ldionne `CMAKE_INSTALL_PREFIX` cannot be used for this purpose. When using the
multiarch layout with the runtimes build, we want to place build artifacts in
`${BUILD_DIR}/{include,lib}/<target>/...` and install them to
`${CMAKE_INSTALL_PREFIX}/{include,lib}/<target>/...`. There are two issues:
1. `CMAKE_INSTALL_PREFIX` only comes into play during install step, but we want
the build layout to match the installation layout so we need a different
variable to control the output directory.
2. We already use `CMAKE_INSTALL_PREFIX` for the toolchain itself and there's
no way to use it hierarchically, that is you cannot do something like
`${SUPER_CMAKE_INSTALL_PREFIX}/{include,lib}/${CMAKE_INSTALL_PREFIX}/...` which
is why we need a separate variable to control the installation directory.
Regarding `LIBCXX_INSTALL_HEADER_PREFIX`, I haven't found any current uses of
that variable. I introduced it in D59168 which was an earlier attempt at having
per-target headers, but D89013 is strictly better for the reasons I described
in https://reviews.llvm.org/D89013#2662578 (no duplicate headers) so I think we
can just remove this variable.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D99484/new/
https://reviews.llvm.org/D99484
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