[llvm-dev] CMake vs. autotools output differences

[Reid Kleckner via llvm-dev]

We have a way to produce a libLLVM.so (
https://llvm.org/bugs/show_bug.cgi?id=15493), but we do not have a way yet
for clang to link against it. It's similar to the situation of clang and
libclang (https://llvm.org/bugs/show_bug.cgi?id=23749).

I really think we just need to push through the cmake jungle and make
libLLVM.so and libclang.so into real libraries consumed by the various LLVM
tools. I think it's the right granularity for most users, even if it's not
right for everyone. It's clearly what distro packagers want.

On Thu, Aug 27, 2015 at 5:58 AM, Andrew Wilkins via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hello,
>
> I've spent some time hacking up the Debian packaging to use CMake instead
> of autotools; it's still a work in progress, but it works. It's a bit of a
> mess, though, primarily because there are differences in the output of the
> CMake and autotools builds.
>
> On my Ubuntu machine, the dependencies for clang-3.6 look like this:
> $ ldd /usr/bin/clang-3.6
>         linux-vdso.so.1 =>  (0x00007ffc7af57000)
>         libLLVM-3.6.so.1 => /usr/lib/x86_64-linux-gnu/libLLVM-3.6.so.1
> (0x00007fe47eac3000)
>         libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0
> (0x00007fe47e8a5000)
>         libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6
> (0x00007fe47e596000)
>         libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1
> (0x00007fe47e380000)
>         libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fe47dfb6000)
>         libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fe47dd9b000)
>         libffi.so.6 => /usr/lib/x86_64-linux-gnu/libffi.so.6
> (0x00007fe47db93000)
>         libedit.so.2 => /usr/lib/x86_64-linux-gnu/libedit.so.2
> (0x00007fe47d959000)
>         libtinfo.so.5 => /lib/x86_64-linux-gnu/libtinfo.so.5
> (0x00007fe47d730000)
>         libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fe47d52c000)
>         libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fe47d224000)
>         /lib64/ld-linux-x86-64.so.2 (0x00007fe480aa5000)
>
> Using CMake with BUILD_SHARED_LIBS, it looks like this:
>     http://paste.ubuntu.com/12205368/
> (the fact that I used pastebin is a hint)
>
> The main difference is the many LLVM/Clang shared library dependencies,
> rather than just one. It's preferred that each shared library is packaged
> separately, but this would be a bit of a maintenance nightmare; so that
> would mean one package with many shared libraries in it (more likely, one
> for all clang shared libraries, and one for all LLVM).
>
> Are the differences between them intentional? Is there any room for change
> -- to have the CMake-build tools link against the monolithic libLLVM as in
> autotools?
>
> Second, Debian packages want both shared objects and static archives.
> BUILD_SHARED_LIBS means one or the other. Is there any reason why it would
> be a bad idea to modify add_llvm_library to create targets for both static
> and shared, if not specified?
>
> Cheers,
> Andrew
>
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>
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