To avoid the affection of my other code, I wrote down this short snippet:
packet.proto:
message packet {
required uint32 var = 1;
}
And pb.cc:
#include "packet.pb.h"
int main()
{
GOOGLE_PROTOBUF_VERIFY_VERSION;
google::protobuf::ShutdownProtobufLibrary();
return 0;
}
If I try to link with libc++, clang++ will complain like this error:
$ clang++ -stdlib=libc++ -o pb pb.cc packet.pb.cc -lprotobuf
Undefined symbols for architecture x86_64:
"google::protobuf::MessageFactory::InternalRegisterGeneratedFile(char
const*, void (*)(std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> > const&))", referenced from:
protobuf_AddDesc_packet_2eproto() in packet-q8y2hq.o
"google::protobuf::DescriptorPool::FindFileByName(std::__1::basic_string<char,
std::__1::char_traits<char>, std::__1::allocator<char> > const&) const",
referenced from:
protobuf_AssignDesc_packet_2eproto() in packet-q8y2hq.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see
invocation)
But everything seems OK without libc++:
$ clang++ -o pb pb.cc packet.pb.cc -lprotobuf
$ otool -L pb
pb:
/usr/local/lib/libprotobuf.7.dylib (compatibility version 8.0.0,
current version 8.0.0)
/usr/lib/libstdc++.6.dylib (compatibility version 7.0.0, current
version 56.0.0)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current
version 169.3.0)
Here are the versions of clang and protobuf:
$ clang -v
Apple clang version 4.1 (tags/Apple/clang-421.11.66) (based on LLVM 3.1svn)
Target: x86_64-apple-darwin12.2.0
Thread model: posix
$ brew info protobuf
protobuf: stable 2.4.1
http://code.google.com/p/protobuf/
/usr/local/Cellar/protobuf/2.4.1 (62 files, 5.9M) *
https://github.com/mxcl/homebrew/commits/master/Library/Formula/protobuf.rb
And I also compiled the snippet on a Linux workstation on which clang and
libc++ were installed. But no error was raised with libc++.
$ /opt/llvm/bin/clang++ -stdlib=libc++ -o pb pb.cc packet.pb.cc -lprotobuf
$ ldd pb
linux-gate.so.1 => (0x005dd000)
libprotobuf.so.7 => /usr/local/lib/libprotobuf.so.7 (0x0035c000)
libc++.so.1 => /usr/lib/libc++.so.1 (0x00113000)
libm.so.6 => /lib/libm.so.6 (0x0072d000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x006ea000)
libc.so.6 => /lib/libc.so.6 (0x00a6c000)
libpthread.so.0 => /lib/libpthread.so.0 (0x001b1000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x001cc000)
librt.so.1 => /lib/librt.so.1 (0x002b7000)
/lib/ld-linux.so.2 (0x008c3000)
As you can see above, I built libc++ on Linux by using libstdc++ as the ABI
layer.
$ clang++ -v
clang version 3.1 (tags/RELEASE_31/final 170526)
Target: i386-pc-linux-gnu
Thread model: posix
libcxx$ svn info
Path: .
URL: http://llvm.org/svn/llvm-project/libcxx/trunk
Repository Root: http://llvm.org/svn/llvm-project
Repository UUID: 91177308-0d34-0410-b5e6-96231b3b80d8
Revision: 170542
Node Kind: directory
Schedule: normal
Last Changed Author: marshall
Last Changed Rev: 170435
Last Changed Date: 2012-12-19 00:46:30 +0800 (Wed, 19 Dec 2012)
Could anybody give some suggestion about this?
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