Bug 1211943

Summary: libclang.so incomplete
Product: [Fedora] Fedora Reporter: Mattias Ellert <mattias.ellert>
Component: llvmAssignee: Adam Jackson <ajax>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 23CC: ajax, bos, dmalcolm, jv+fedora, petersen, scottt.tw
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Last Closed: 2016-06-05 12:11:38 UTC Type: Bug
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Blocks: 1210948    

Description Mattias Ellert 2015-04-15 09:05:03 UTC 
Description of problem:

I am trying to package a project for Fedora that uses the llvm and clang libraries. The build instructions for the project uses the static llvm and clang libraries, and compiling using these instructions work.

When I try to replace the static library linking with shared library linking, this works fine for the llvm libraries. If I replace the long list of static llvm libraries with the single libLLVM shared library in the build instructions this works.

However, if I then try the next step and try to replace the list of static clang libraries with the libclang.so shared library the linking fails with a lot of missing symbols. It looks like the libclang.so is incomplete and doesn't contain everthing that the static libraries contain.

Version-Release number of selected component (if applicable):

llvm-3.6.0-1.fc23.x86_64
llvm-devel-3.6.0-1.fc23.x86_64
llvm-static-3.6.0-1.fc23.x86_64
clang-3.6.0-1.fc23.x86_64
clang-devel-3.6.0-1.fc23.x86_64

How reproducible:

Always

Steps to Reproduce:

See my attempt to use the libclang.so shared library in this SRPM:
http://www.ellert.se/castxml-0.1-0.1.20150414git43fa139.fc23.src.rpm

Actual results:

Failed linking when using shared libraries

Expected results:

Successful linking when using shared libraries

Additional info:

Why does clang-devel depend on clang? The package I am trying to build links to the clang library and needs the clang headers in clang-devel at runtime but it deas not need the clang and llvm binaries and everything that gets dragged in by installing them. The dependency on clang in clang-devel causes a dependency bloat.
Comment 1 Jan Kurik 2015-07-15 14:16:25 UTC 
This bug appears to have been reported against 'rawhide' during the Fedora 23 development cycle.
Changing version to '23'.

(As we did not run this process for some time, it could affect also pre-Fedora 23 development
cycle bugs. We are very sorry. It will help us with cleanup during Fedora 23 End Of Life. Thank you.)

More information and reason for this action is here:
https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora23
Comment 2 Jan Včelák 2016-06-05 12:11:38 UTC 
I think this problem is caused by the default linker behavior on Fedora.

https://fedoraproject.org/wiki/UnderstandingDSOLinkChange

The code you want to link is present in some libclang*.so library insted of libclang.so. libclang.so links to the "side" libraries but these dependencies are not added to your program.

% cat main.cc 
#include <clang/Format/Format.h>

int main(int argc, char *argv[])
{
	clang::format::getLLVMStyle();
	return 0;
}
% g++ -lclang ./main.cc      
/usr/bin/ld: /tmp/fcelda/cc6A7cYr.o: undefined reference to symbol '_ZN5clang6format12getLLVMStyleEv'
/usr/lib64/libclangFormat.so: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status

You need to link explicitly:

% g++ -lclangFormat ./main.cc
% echo $?
0

Or copy the indirect dependencies when linking (but be careful with that):

% g++ ./main.cc -Wl,--copy-dt-needed-entries -lclang
% echo $?
0