** Description changed:
+ SRU acceptance criteria: the example successfully links.
+
On updating ubuntu from 15.04 to 15.10, I see changes in how clang
resolves references to some libraries. (I think this is not an ubuntu
question but rather a clang question and that I've missed some subtlety
on how clang has recently changed. I suspect initially that this is
related to the gcc-5 ABI changes, but I'm not sure how to proceed.)
Here's a tiny test example designed only to tickle the phenomenon:
#include <jsoncpp/json/json.h>
#include <iostream>
int main(int argc, char *argv[]) {
- std::cout << argc << " - " << argv[0] << std::endl;
- Json::Reader reader;
- Json::Value root;
- reader.parse("", root, false);
- std::cout << reader.getFormattedErrorMessages() << std::endl;
- return 0;
+ std::cout << argc << " - " << argv[0] << std::endl;
+ Json::Reader reader;
+ Json::Value root;
+ reader.parse("", root, false);
+ std::cout << reader.getFormattedErrorMessages() << std::endl;
+ return 0;
}
If I compile like this
clang++ -ggdb3 -Wall -Wextra -std=c++14 -o json_test json_test.cc
-ljsoncpp
/tmp/json_test-680d3a.o: In function `main':
/tmp/json_test.cc:10: undefined reference to
`Json::Reader::getFormattedErrorMessages() const'
clang: error: linker command failed with exit code 1 (use -v to see
invocation)
And yet the definition appears to be present:
jeff@birdsong:src $ objdump -TC /usr/lib/x86_64-linux-gnu/libjsoncpp.so |
grep getFormatted
000000000000e190 g DF .text 00000000000004d2 Base
Json::OurReader::getFormattedErrorMessages[abi:cxx11]() const
000000000000dc70 g DF .text 00000000000004d2 Base
Json::Reader::getFormattedErrorMessages[abi:cxx11]() const
- jeff@birdsong:src $
+ jeff@birdsong:src $
The abi:cxx11 suggests I might at least try this
clang++ -ggdb3 -Wall -Wextra -std=c++11 -o json_test json_test.cc
-ljsoncpp
but same error. On the other hand, this works fine:
g++ -ggdb3 -Wall -Wextra -std=c++14 -o json_test json_test.cc -ljsoncpp
Fwiw, here's version info:
jeff@birdsong:tmp $ g++ --version
g++ (Ubuntu 5.2.1-22ubuntu2) 5.2.1 20151010
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
jeff@birdsong:tmp $ clang++ --version
Ubuntu clang version 3.6.2-1 (tags/RELEASE_362/final) (based on LLVM 3.6.2)
Target: x86_64-pc-linux-gnu
Thread model: posix
jeff@birdsong:tmp $
ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: libjsoncpp-dev 0.10.5-1
ProcVersionSignature: Ubuntu 4.2.0-16.19-generic 4.2.3
Uname: Linux 4.2.0-16-generic x86_64
ApportVersion: 2.19.1-0ubuntu3
Architecture: amd64
CurrentDesktop: i3
Date: Mon Oct 26 12:00:40 2015
Dependencies:
- gcc-5-base 5.2.1-22ubuntu2
- libc6 2.21-0ubuntu4
- libgcc1 1:5.2.1-22ubuntu2
- libjsoncpp0v5 0.10.5-1
- libstdc++6 5.2.1-22ubuntu2
+ gcc-5-base 5.2.1-22ubuntu2
+ libc6 2.21-0ubuntu4
+ libgcc1 1:5.2.1-22ubuntu2
+ libjsoncpp0v5 0.10.5-1
+ libstdc++6 5.2.1-22ubuntu2
EcryptfsInUse: Yes
InstallationDate: Installed on 2015-10-23 (2 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
SourcePackage: libjsoncpp
UpgradeStatus: Upgraded to wily on 2015-10-23 (2 days ago)
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https://bugs.launchpad.net/bugs/1510042
Title:
linking against -ljsoncpp fails with clang
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