I am using Kubuntu 14.04, and installed the FreeImage library with
sudo apt-get install libfreeimage-dev
As far as I can tell, it is correctly installed, with FreeImage.h in /usr/include and libfreeimage.a in /usr/lib. However, this trivial C program
#include <FreeImage.h>
int main(int argc, char **argv) {
FreeImage_Initialise(FALSE);
FreeImage_DeInitialise();
return 0;
}
fails to compile. Running
gcc -lfreeimage fitest.c -o fitest
outputs
/tmp/ccFbb0HQ.o: In function `main':
fitest.c:(.text+0x15): undefined reference to `FreeImage_Initialise'
fitest.c:(.text+0x1a): undefined reference to `FreeImage_DeInitialise'
collect2: error: ld returned 1 exit status
What am I doing wrong?
This wouldn't normally be the case with shared libraries but only static ones, but I'm going to give it a shot anyway since it matches your symptoms, and you also mention libfreeimage.a instead of libfreeimage.so, indicating that you're trying to use the static library.
When linking against static libraries, you need to give the library arguments after the explcit source/object arguments to the compiler, because the compiler will only process yet unresolved symbols from the library:
gcc -o fitest fitest.c -lfreeimage
If you give a static library argument before any source/object arguments, then, no symbols will yet be unresolved, nothing will be picked from the library, and the symbols will instead be seen as unresolved at the end.