GCC Linker prefixes flatcc's flatcc_builder_init function with an underscore and does not link

[thomasa...@gmail.com]

Hello everyone,

I'm making my way through the flatbuffers tutorial for C and I can't make it very far unfortunately. I've pasted the sample code into my project:

#include "flatbuffers/StarBuffer_builder.h"

#include "flatbuffers/flatcc_builder.h"
...

...

        flatcc_builder_t builder, *B;

        B = &builder;

        // Initialize the builder object.

        flatcc_builder_init(B);

zmq_cpub $./build.sh

Undefined symbols for architecture x86_64:

  "_flatcc_builder_init", referenced from:

      _main in publisher-d532f6.o

ld: symbol(s) not found for architecture x86_64

clang: error: linker command failed with exit code 1 (use -v to see invocation)

Here's my build command: gcc publisher.c -o bin/zmq_pub -lczmq -lzmq

I'm on OSX. Here are my GCC details:

zmq_cpub $gcc --version

Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1

Apple LLVM version 8.0.0 (clang-800.0.38)

Target: x86_64-apple-darwin15.6.0

Thread model: posix

InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Any idea why GCC is adding the underscore?

[thomasa...@gmail.com]

Will update my own thread for posterity's sake. I had already used brew to install flatcc:

"brew install flatcc"

But I was not linking the library in like I was the ZMQ I had integrated earlier. Here's my updated build command:

gcc publisher.c -o bin/zmq_pub -lzmq -lflatcc

In my source I have the following imports:

#include "flatbuffers/StarBuffer_builder.h" // generated header file from my StarBuffer.fbs file

#include "flatbuffers/flatbuffers_common_builder.h"

Inside my flatbuffers folder I have:

 flatbuffers $ls

StarBuffer_builder.h StarBuffer_verifier.h flatbuffers_common_reader.h

StarBuffer_reader.h flatbuffers_common_builder.h

All good now!

[mikkelfj]

On Wednesday, October 19, 2016 at 5:56:14 PM UTC+2, thomasa...@gmail.com wrote:

Will update my own thread for posterity's sake. I had already used brew to install flatcc:

"brew install flatcc"

But I was not linking the library in like I was the ZMQ I had integrated earlier. Here's my updated build command:

gcc publisher.c -o bin/zmq_pub -lzmq -lflatcc

 

Good to hear that you solved it.

Most likely you want to link with -lflatccrt and not -lflatcc because the runtime library is much smaller. -lflatcc is used if you want to compile flatbuffer schema from within you application. But then again, the linker is probably smart enough to only take what it needs.