I have been using C to code for sometime and I had no issues in compiling and linking my code to archive libraries (.a files). However, now I need to switch to C++ and doing so, I have to use g++ instead of cc for linking and compiling.
Using C, first thing to do was compiling the source and creating the object file and then linking it to the library using the same command but without the -c option:
cc -c -ggdb -Wall -Werror -I.. test.c -o test.o
cc -o test -ggdb -Wall -Werror test.o ../libpmem/libpmem.a
As I think the same procedure should be done for doing the same thing with g++, I tried to change the compiling and linking phase as follow:
g++ -c -ggdb -Wall -Werror -I.. test.c -o test.o
g++ test.o -I.. -L/path/libpmem -lpmem -o test
Although both sets should do the same thing, I always get an error while trying to link using g++. Here is the error message:
test.o: In function `main':
/path/test/test.c:5: undefined reference to `pmem_msync_mode()'
collect2: ld returned 1 exit status
make: *** [all] Error 1
There must be something wrong with the linking phase as the method definition must be found in the library file (just as the cc linker can find the definition and do the linking without any problem).
I also tried to do both linking and compiling using a single g++ command, but no matter what I do, I always get the same error. Any idea how can I fix this?
you probably have some sort of name mangling problem...
since it looks like that is declared in a c library there should already be some sort of
#ifdef __cplusplus
extern "C" {
#endif
int pmem_msync_mode();
#ifdef __cplusplus
}
#endif
but if there isn't in the library header you may have to do something like;
extern "C" {
#include <pmem.h>
}