c++ Calling functions across multiple .cpp files?

Question

I have 3 files: - main.cpp - other.cpp - other.h

I am trying to call a function that was declared in other.h, from main.cpp, with the code being written in other.cpp

My code:

main.cpp:

//#Allmyincludes
#include "other.h"

int main(int argc, const char *argv[])
{
    const char *file = argv[1];
    read(file);
    return 0;
}

other.cpp:

//#Allmyincludes
#include "other.h"

void read(const char *file)
{
    //code
}

other.h:

void read(const char *file);

The error I get is:

main.cpp:(.text+0x44): undefined reference to 'read(char const*)'

Within read(), I am using main::variableName to access variables from within main (no errors), however I just can't get the function call to work. If I try to do other::read(file); that also doesn't work because :: is for functions and not files. It gives me the error: 'other' has not been declared.

Any explanation as to why my header file/call isn't working is greatly appreciated.

Show your compilation command. If using GCC (i.e. g++) notice that order of program arguments to the compiler matters a big lot. — Basile Starynkevitch
– Basile Starynkevitch, Commented Oct 11, 2013 at 14:04

john · Accepted Answer · 2013-10-11 14:04:32Z

1

There are many causes of undefined reference errors. In your case, from what you've described, the likeliest is that you haven't compiled other.cpp

You need to add other.cpp to your project/makefile/command line.

For more detailed help you probably need to explain how you are building your program. There is nothing actually wrong with the code, it's the way you build your program that is the issue.

answered Oct 11, 2013 at 14:04

john

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1 Comment

user2871213 Over a year ago

Thank you. I only had g++ main.cpp -Wall -o main

Pavlo Vons · Accepted Answer · 2013-10-11 14:24:24Z

0

try

gcc -Wall main.cpp other.cpp -o mymain

answered Oct 11, 2013 at 14:24

Pavlo Vons

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