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User forums => Using Code::Blocks => Topic started by: Lowkus on July 11, 2016, 09:19:29 am

Title: Linking .cpp and .h
Post by: Lowkus on July 11, 2016, 09:19:29 am

Is CodeBlocks supposed to automatically know to link a .cpp file if the matching .h file is #included?

I have a redgloves.h file in the project with this line:
  extern const unsigned char RedGloves_png[5];

And a redgloves.cpp file in the project with this line:
  const unsigned char RedGloves_png[5] = {48,49,50,51,52};

And a main.cpp file in the project with these lines:
  #include "redgloves.h"
  wxMemoryInputStream istream(RedGloves_png, sizeof RedGloves_png);

When I attempt to compile it throws the error "undefined reference to RedGloves_png".  If I cut the line from RedGloves.cpp and put it into the RedGloves.h file, then everything compiles without error.  I don't think I should have to move it out of the RedGloves.cpp file.

Title: Re: Linking .cpp and .h
Post by: raynebc on July 11, 2016, 09:45:46 am

If you're working with multiple source/header files, create a project containing all of them.

Title: Re: Linking .cpp and .h
Post by: BlueHazzard on July 11, 2016, 11:53:23 am

http://wiki.codeblocks.org/index.php?title=FAQ-Compiling_(general)#Q:_How_do_I_report_a_compilation_problem_on_the_forums.3F

Title: Re: Linking .cpp and .h
Post by: Lowkus on July 12, 2016, 08:56:25 pm

The files are all within one project.

Here's the build log:

Build started on: 12-07-2016 at 11:52.08
Build ended on: 12-07-2016 at 11:52.25
-------------- Build: Debug in cshp (compiler: GNU GCC Compiler)---------------
mingw32-g++.exe -Wall -pipe -mthreads -D__GNUWIN32__ -D__WXMSW__ -DwxUSE_UNICODE -g -std=c++14 -IC:\wxWidgets-3.1.0\include -IC:\wxWidgets-3.1.0\lib\gcc_dll\mswu -c C:\Users\Mark\Documents\cProjects\Cshp\cshpApp.cpp -o obj\Debug\cshpApp.o
mingw32-g++.exe -Wall -pipe -mthreads -D__GNUWIN32__ -D__WXMSW__ -DwxUSE_UNICODE -g -std=c++14 -IC:\wxWidgets-3.1.0\include -IC:\wxWidgets-3.1.0\lib\gcc_dll\mswu -c C:\Users\Mark\Documents\cProjects\Cshp\cshpMain.cpp -o obj\Debug\cshpMain.o
mingw32-g++.exe -Wall -pipe -mthreads -D__GNUWIN32__ -D__WXMSW__ -DwxUSE_UNICODE -g -std=c++14 -IC:\wxWidgets-3.1.0\include -IC:\wxWidgets-3.1.0\lib\gcc_dll\mswu -c C:\Users\Mark\Documents\cProjects\Cshp\redgloves.cpp -o obj\Debug\redgloves.o
windres.exe -IC:\wxWidgets-3.1.0\include -IC:\wxWidgets-3.1.0\lib\gcc_dll\mswu -Iresources -J rc -O coff -i C:\Users\Mark\DOCUME~1\CPROJE~1\Cshp\resource.rc -o obj\Debug\resource.res
mingw32-g++.exe -LC:\wxWidgets-3.1.0\lib\gcc_dll -o bin\Debug\CShp.exe obj\Debug\cshpApp.o obj\Debug\cshpMain.o obj\Debug\redgloves.o obj\Debug\resource.res -mthreads -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -luuid -lcomctl32 -lwsock32 -lodbc32 -lwxmsw31u -mwindows
obj\Debug\cshpMain.o: In function "ZN9cshpFrame14OnButton1ClickER14wxCommandEvent':
C:/Users/Mark/Documents/cProjects/Cshp/cshpMain.cpp:149: undefined reference to "RedGloves_png'
collect2.exe: error: ld returned 1 exit status
Process terminated with status 1 (0 minute(s), 16 second(s))
2 error(s), 0 warning(s) (0 minute(s), 16 second(s))

Title: Re: Linking .cpp and .h
Post by: BlueHazzard on July 12, 2016, 11:14:23 pm

i can't reproduce this with a minimal example...

if i create a project with the following files:
a.cpp

Code

#include "a.h"

const int test[5] = {42,43,44,45,46};

a.h

Code

extern const int test[5];

main.cpp:

Code

#include <iostream>
#include "a.h"

using namespace std;

int main()
{
    cout << "Hello world!" << endl;
    cout << test[3] << endl;
    return 0;
}

compiling (i made the main.cpp compiling weight lower, so it gets compiled earlier, like in your project:

Code

[ 33.3%] mingw32-g++.exe -Wall -fexceptions -g -std=gnu++11 -Wno-unused-local-typedefs -Wno-deprecated-declarations  -c ###\main.cpp -o obj\Debug\main.o
[ 66.7%] mingw32-g++.exe -Wall -fexceptions -g -std=gnu++11 -Wno-unused-local-typedefs -Wno-deprecated-declarations  -c ###\fghhh\a.cpp -o obj\Debug\a.o
[100.0%] mingw32-g++.exe  -o bin\Debug\fghhh.exe obj\Debug\main.o obj\Debug\a.o   
Output file is bin\Debug\fghhh.exe with size 1.01 MB
Process terminated with status 0 (0 minute(s), 0 second(s))
0 error(s), 0 warning(s) (0 minute(s), 0 second(s))
Build log saved as: 

all fine,
also your coding style is ok (http://stackoverflow.com/questions/1433204/how-do-i-use-extern-to-share-variables-between-source-files-in-c)

so there has to be something else...
can you try to replicate this with a minimal example?

greetings

Title: Re: Linking .cpp and .h
Post by: Lowkus on July 12, 2016, 11:26:07 pm

That link helped.  I had #Include "redgloves.h" in the main cpp file, but not in the redgloves.cpp file.  After adding that include to redgloves.cpp the project compiled successfully.  Thanks!