undefined reference `rtc::FatalMessage::FatalMessage(char const*, int, std::string*)' link v62

[Ankur Deep Jaiswal]

Hi,

 i am trying to build webrtc version 62 , using the following

1.git checkout -b branch62 refs/remotes/branch-heads/62

2.gn gen out_release_62/x64/Debug --args="rtc_include_tests=false rtc_use_h264=false use_rtti=true is_component_build=false enable_iterator_debugging=false enable_nacl=false target_os=\"linux\" target_cpu=\"x64\" is_debug=true"

3.ninja -C out_release_62/x64/Debug

i am linking to libwebrtc.a and libwebrtc_common.a

but wherever i try to use RTC_CHECK_EQ or RTC_DCHECK_LT i get the the following error:-  undefined reference to `rtc::FatalMessage::FatalMessage(char const*, int, std::string*)'

and 

out_release_62/include/webrtc/rtc_base/checks.h:176: undefined reference to `std::string* rtc::MakeCheckOpString<int, int>(int const&, int const&, char const*)'

./src/testwebrtc.o: In function `rtc::CheckLtImpl(int, int, char const*)':

i had no issue with build branch head 59 , 

i tried linking to librtc_base.a and librtc_base_approved.a but no luck, 

any pointers for me

[Ankur Deep Jaiswal]

A sample program that produces this error is 

#include <iostream>

#include <string>

#include <webrtc/rtc_base/checks.h>

#include <webrtc/rtc_base/ssladapter.h>

#include <webrtc/rtc_base/logging.h>

#include <webrtc/api/peerconnectioninterface.h>

using namespace std;

int main() {

cout << "!!!Hello World!!!" << endl; // prints !!!Hello World!!!

std::string type;

std::string sdp;

webrtc::SdpParseError error;

webrtc::CreateSessionDescription(type,sdp,&error);

RTC_DCHECK(5);

RTC_CHECK_EQ(1,6);

RTC_DCHECK_LT(1,4);

return 0;

}

gcc verison 6.3 linker

g++ -L/home/test/webrtc-checkout-ankur/src/out_release_62/x64/Debug -o "testwebrtc"  ./src/testwebrtc.o   -lwebrtc -lwebrtc_common -lpthread -lm -ldl

this is the error that is returned

./src/testwebrtc.o: In function `main':

/home/test/workspace/testwebrtc/Debug/../src/testwebrtc.cpp:22: undefined reference to `webrtc::CreateSessionDescription(std::string const&, std::string const&, webrtc::SdpParseError*)'

/home/test/workspace/testwebrtc/Debug/../src/testwebrtc.cpp:24: undefined reference to `rtc::FatalMessage::FatalMessage(char const*, int, std::string*)'

/home/test/workspace/testwebrtc/Debug/../src/testwebrtc.cpp:25: undefined reference to `rtc::FatalMessage::FatalMessage(char const*, int, std::string*)'

./src/testwebrtc.o: In function `rtc::CheckEqImpl(int, int, char const*)':

makefile:45: recipe for target 'testwebrtc' failed

/home/test/webrtc-checkout-ankur/src/out_release_62/include/webrtc/rtc_base/checks.h:176: undefined reference to `std::string* rtc::MakeCheckOpString<int, int>(int const&, int const&, char const*)'

./src/testwebrtc.o: In function `rtc::CheckLtImpl(int, int, char const*)':

/home/test/webrtc-checkout-ankur/src/out_release_62/include/webrtc/rtc_base/checks.h:179: undefined reference to `std::string* rtc::MakeCheckOpString<int, int>(int const&, int const&, char const*)'

collect2: error: ld returned 1 exit status

[Ankur Deep Jaiswal]

From my observation any function/method that has std::string in it is showing this behaviour

[Ankur Deep Jaiswal]

I have successfully solved the issue, for all those poor souls who come across this, 

the explanation is very simple.

WebRTC builds itself using clang, it also by default uses libc++ bundled with clang, which postfixes every std namespace with __1, so std::string in g++ is std::string and in clang is std::__1::string,

so this will result in the application not linking properly to libwebrtc.a,

there are two solutions to this, 

1. use -stdlib=libc++ in your app, or

2. build webrtc using libstdc++, that can be done by passing use_custom_libcxx=false and use_custom_libcxx_for_host=false to the gn gen args.

this was tested on an ubuntu 16.04 OS with GCC 5.4 

[Alexandre GOUAILLARD]

thank you for finding the solution, and giving credits.

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--

Alex. Gouaillard, PhD, PhD, MBA

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President - CoSMo Software Consulting, Singapore

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sg.linkedin.com/agouaillard

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[Ankur Deep Jaiswal]

Hey Alex nothing like that, just an honest mistake. Please forgive me if you think I was taking it away from you. If I did mean something like that I would not given you bounty. I just did not know how to link two platforms. I did not even know you were here.

I had no reason to duplicate this information here, but that it would help someone else from the same fate.

Please forgive me if I hurt you.

> To unsubscribe from this group and stop receiving emails from it, send an email to discuss-webrt...@googlegroups.com.