I seem to be forgetting my C++ …
I’m trying to declare some functions in C in separate sources, and including the appropriate .h when necessary. It compiles OK; but the problem is during linking, where the linker complains about functions already being defined.
I even tried defining the functions as extern, in a (vain) attempt to just declare the functions and let the implementation come true only on the .c.
This is an abridged description of my code:
common.h
#include <stdio.h> module1.h
#include 'common.h' #ifndef MODULE1_H_ #define MODULE1_H_ int init(int option); int open(char* db, char* username, char* password); int get(int handler, int date[2], int time[2], int* data, int& rowsize, int& numrows); int put(int handler, int* data, int& datasize, int& numrows); int close(int handler); int finalize(); #endif /* MODULE1_H_ */ module2.h
#include 'common.h' #ifndef MODULE2_H_ #define MODULE2_H_ int get1(int handler, int date, int time, int *data, int& datasize, int& rowsize); int put1(int handler, int* data, int datasize); #endif /*MODULE2_H_*/ module1.cpp
#include 'module1.h' int init(int option) { ... } int finalize() { ... } int get(int handler, int date[2], int time[2], int* data, int& rowsize, int& numrows) { .... } ... module2.cpp
#include 'module1.h' #include 'module2.h' int get1(int handler, int date, int time, int* data, int rowsize) { int daterange[2]={date,date}; int timerange[2]={time,time}; int rsize, numrows, result; result=get(handler, daterange,timerange, data, rsize, numrows); rowsize=rsize; if(numrows!=1) printf('Uh oh...\n'); return result; } ... Compilation & linkage:
g++ -o module1.o -c module1.cpp g++ -o module2.o -c module2.cpp g++ -fPIC -shared -o library.so module1.o module2.o As I said, it compiles OK. The problem is during linkage, where the linker ‘sees’ that there are two implemented functions from module1.h: one from the inclusion of module1.h in module1.cpp; and the other from the inclusion of module1.h together with module2.h in module2.cpp.
I know the functions are supposed to be declared, but I’m obviously doing a faux-pas. Could someone please point out where it is? Thank you in advance.
Thank you all for your replies and comments. I figured out the problem (it turned out to be a very stupid thing) and am close to solving it (hopefully).
It turns out it comes from another include file (cfortran.h) which implements a layer for using C function calls in Fortran (and vice-versa). It’s very useful and I’ve been using it with success up until now, but I was ‘blinded’ by the errors; that include’s documentation states that care should be taken when using it in C++ context (not in C) but this is the first instance where that warning actually produces effects.
Thank you once more for your help.