[llvm-dev] OpenCL runtimes and LLVM command line options

[Heinz Wiesinger via llvm-dev]

Hello everyone,

A while back I hit an issue where the presence of multiple OpenCL runtimes 
on a single system triggered errors in libLLVM caused by redeclaring 
command line arguments [0]. There's been some discussion on the bug report and 
a pointer to a slightly older report, unrelated to OpenCL, but most likely 
about the same issue [1].

OpenCL uses an ICD loader library to abstract away the installed runtimes. 
That way, applications can link against the ICD loader instead of the actual 
runtimes, which makes it more portable. This does also allow distributions to 
ship support for all the various OpenCL runtimes out there.

The problem is that some OpenCL runtimes link libclangCodeGen statically 
(where the offending cli arguments are defined), and libLLVM dynamically.

The ICD loader has to load every runtime on the system in order to determine 
which one to use. When an affected runtime is loaded, it registers the cli 
arguments from the static libclangCodeGen in the dynamic libLLVM. If another 
runtime is loaded that tries to do the same, the check in libLLVM triggers and 
aborts program execution.

The practical effect that users see is, once multiple OpenCL runtimes are 
installed on one system any OpenCL-enabled application aborts on start with an 
LLVM error. Needless to say this is a less than desirable situation.

There are currently multiple workarounds for this problem, each with its own 
set of drawbacks. Debian decided to statically link libLLVM [2], OpenSUSE 
decided to build all clang libs also as shared libraries (using 
BUILD_SHARED_LIBS=ON) [3] and Red Hat has an open issue about it in their bug 
tracker [4].

Since this issue has been present for a rather long time without clear 
solution or recommendation for a workaround, I'd like to bring this some more 
attention in the hopes of fixing this.

Grs,
Heinz

[0] https://bugs.llvm.org/show_bug.cgi?id=30587
[1] https://bugs.llvm.org/show_bug.cgi?id=22952
[2] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=852746
[3] https://bugzilla.opensuse.org/show_bug.cgi?id=1065464
[4] https://bugzilla.redhat.com/show_bug.cgi?id=1565659
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 228 bytes
Desc: This is a digitally signed message part.
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180506/aafac27c/attachment.sig>