linking g++ code with shared library build with gcc

Question

I made shared library using gcc . I would like to link this library using g++ comiler with source code *.c. Example

test_init.c #include<stdio.h> int test_init() { printf(" test init success\n"); return 0; }

gcc -shared -o libtest.so test_init.c

test.c

#include<stdio.h> extern int test_init(); main() { test_init(); }

g++ -I. -L. -ltest test.c

/tmp/ccuH5tIO.o: In function main': test.c:(.text+0x7): undefined reference totest_init()' collect2: ld returned 1 exit status

Note: If i compile test.c with gcc it works, but i would like to use this approach due to other dependencies. Is it possible??

Dirk is no longer here · Accepted Answer · 2011-03-10 02:02:24Z

You call C routines from C++ by declaring them

 extern "C" { .... }

Look into a few header files on your system or Google around -- that's the only way to do it because of different function signature systems between the languages.

I tried that but didn't work. in this case both are c files but the executable is making with g++ compiler

Erik · Accepted Answer · 2011-03-10 02:20:04Z

1

As Dirk said, change extern int test_init(); to extern "C" { int test_init(); }

answered Mar 10, 2011 at 2:20

Erik

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Comments

Dmitry Yudakov · Accepted Answer · 2011-03-10 09:32:21Z

Usually -llibrary should be after object files or c/c++ files in gcc command line

g++ -I. -L. test.c -ltest

The linker searches for the symbols mentioned in test.c after it's processed and when you put -llib before test.c, it's just unable to find them.

See man ld for more info.

Not sure how the things are when you use extern, perhaps something is different in this case.

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