C++ Linux Error Loading Shared Library `undefined symbol: pthread_create`

Question

I have created a library that compiles well and everything. The library file is "libTextSearch.so"

Inside the library, it creates a thread. I am using C++11 threads for this:

TextSearch::TextSearch(){
    std::thread t(&TextSearch::ThreadProc, this);
    t.detach();
}

As I said, the library compiles and I have the libTextSearch.so file.

I am trying to load the library in a different application:

void* handle = dlopen("libTextSearch.so", RTLD_LAZY);
if(!handle){
    //std::cout << "\n  Failed to load libTextSearch.so\n\n";
    fprintf(stderr, "dlopen failed: %s\n", dlerror());
    return 1;
}

I have the package copied to /usr/lib already. This is the output I get:

dlopen failed: /usr/lib/libTextSearch.so: undefined symbol: pthread_create
RUN FINISHED; exit value 1; real time: 0ms; user: 0ms; system: 0ms

I have looked up this question. I think it is related, but I have no idea of applying that to my situation.

Any ideas?

score 1 · Answer 1 · answered Mar 20 '17 at 19:37

1

I can't exactly be sure since I don't know how you are building this project, or how libTextSearch.so is built, but you need to link against libpthread somehow when generating libTextSearch. Typically in your build environment you would supply -lpthread as an argument to dynamically link to it.

gcc -c testsearch.cpp -lpthread -o textsearch.o

for example

answered Mar 20 '17 at 19:37

Keith k

63
7

Thanks this resolved the loading issue, however, i am facing another issue with `std::thread t(&TextSearch::ThreadProc, this);`. It causes runtime error as it doesnt like being treated not as `pthread`. Any clue? – Everyone Mar 20 '17 at 22:02
Thanks for the answer, Rama's answer fixed everything for me – Everyone Mar 21 '17 at 15:40
@Everyone Happy coding friend – Keith k Mar 21 '17 at 20:42

Rama · Accepted Answer · 2017-03-21T14:45:23.207

1

Just dlopen thread library beforehand with RTLD_GLOBAL

void* handlePthread = dlopen("libpthread.so.0", RTLD_GLOBAL | RTLD_LAZY);
if(!handlePthread ){
    //std::cout << "\n  Failed to load libpthread.so.0\n\n";
    fprintf(stderr, "dlopen failed: %s\n", dlerror());
    return 1;
}

edited Mar 21 '17 at 14:45

answered Mar 20 '17 at 20:08

Rama

3,222
2
11
26

This is what i had: `dlopen failed: libpthread.so.0: invalid mode for dlopen(): Invalid argument` – Everyone Mar 20 '17 at 22:04
@Everyone EDITED, test open it with `| RTLD_LAZY` please – Rama Mar 21 '17 at 14:45
THANK YOU! Fixed all my problems – Everyone Mar 21 '17 at 15:37

C++ Linux Error Loading Shared Library `undefined symbol: pthread_create`

2 Answers2