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Yes, I know there's already several questions that go into detail about this, but I feel like my question isn't that detail-specific. Just something staring at me in the face, but I can't quite see it.

I'm compiling C and C++ files together in a Makefile. Everything seems to be running fine until I get the titular error, which pertains to the functions in CFile2.

Compilation works like this (w/ placeholder names):

g++ -c main.cpp g++ -c Class.cpp gcc -c CFile1.c gcc -c CFile2.c g++ main.o Class.o CFile1.o CFile2.o -lcurl

My Class.cpp has a Class.hpp, and my CFile1 and CFile2 both have .h files respectively. Everything is located within the same directory, and they all have the same header guard structure. 

#ifndef #define //Insert function prototypes here #endif

I'm also only including the CFile1.h and CFile2.h in Class.hpp. Is there something I'm missing based on this info only?

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  • maybe look at this answer: stackoverflow.com/questions/16850992/… ... Also, #pragma(once) (you may have to google it) is nicer than those include guards... Commented Sep 3, 2015 at 21:39
  • #pragma once works if your build environment A) uses a compiler that supports it (most seem to these days, but it fails silently if the build system does not) and B) does not use network mounted drives or symlinks. Commented Sep 3, 2015 at 22:01

1 Answer 1

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Maybe you are missing the extern "C" in the c header?

If you compile c file and want to link with c++ you mast add extern "C", but the c compiler doesn't recognize it so it must is the #ifdef __cplusplus

Add at the beginning of the header, before functions deceleration: 

#include <stdio> // and all other includes... #ifdef __cplusplus extern "C" { #endif void funnction_name1(); //sample 1 int funnction_name2(char* p); //sample 2 //must close the extern "C" block #ifdef __cplusplus } #endif

you can also add it before each function as follows:

 #ifdef __cplusplus extern "C" #endif // no block for the extern "C", so it applied only for a single function void funnction_name(); //a sample func.
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Thank you. This works perfectly.

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