[PATCH] D63637: Do not set an RPATH on statically-linked LLVM executables.

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

> This RPATH breaks the ability to run executables from the build area if
>  the host compiler provides a libc++ and we also build an
>  ABI-incompatible libc++ as part of the same monorepo compilation.

This is the RPATH we set:

  set(_install_rpath "\$ORIGIN/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})

I believe LLVM_LIBDIR_SUFFIX is typically empty.

This is a pretty normal convention, and it should work from the build directory and the install directory. It just says, if there are shared libraries, go to ${root}/bin/../lib/ and search for any shared libs there first.

I think maybe we shouldn't build libc++, and any other shared libraries that might conflict with system shared libraries, into ${builddir}/lib. Don't we install libcxx into lib/clang/9.0.0/lib/... in the end anyway, or is libcxx not treated as a compiler runtime library?



================
Comment at: llvm/cmake/modules/AddLLVM.cmake:756
 
-  if(NOT ARG_NO_INSTALL_RPATH)
-    llvm_setup_rpath(${name})
+  if (LLVM_LINK_LLVM_DYLIB AND NOT ARG_DISABLE_LLVM_LINK_LLVM_DYLIB)
+    set(USE_SHARED USE_SHARED)
----------------
mgorny wrote:
> I think this is also needed when building with `BUILD_SHARED_LIBS`. Possibly also when the target explicitly links to one of the shared-only libraries.
Yep.


================
Comment at: llvm/cmake/modules/AddLLVM.cmake:758
+    set(USE_SHARED USE_SHARED)
+    if(NOT ARG_NO_INSTALL_RPATH)
+      llvm_setup_rpath(${name})
----------------
chandlerc wrote:
> Just to make sure I understand correctly, *any* time we build a shared library of some form, we'll get here? Even if its `libclang.so` or some such?
> 
> Provided I've understood correctly, then this make sense. However, I wonder, won't this still fail for things like c-index-test?
I think we only come here for executables, but yes, your concern about `c-index-test` seems warranted. In the standard, static configuration, libclang seems to be a shared library, and c-index-test links to it. Without the rpath, it probably won't find it. But, this code sets the "install rpath", and I think cmake actually goes back and tweaks the rpath when it does the install step, so maybe this won't affect that.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D63637/new/

https://reviews.llvm.org/D63637