Programming Forums > Application Development > C++

c0ldshadow · Sep 16th, 2005, 4:03 PM

hey folks,i havent been doing that much programming over the last few months but ive gotten back into working on some stuff recently. basically the issue i'm having is that im getting a program to compile even though it shouldnt (at least i think).

i have a libgenericwipe project that contains a .cpp,.h,and .dev file in it. this libgenericwipe has not even been compiled to generate any static link libraries.

in a separate folder i have another project for the executable im making.. this project includes the .h file for libgenericwipe. in the linker section for this project, i am linking to nothing.

the program compiles without any errors or linker errors and i am able to call the genericwipe function even without linking to anything..

my guess is im missing something very obvious or im just being stupid.

here are the contents of my project files..

killer.cpp

(Toggle Plain Text)

#include <windows.h>
#include "c:\\c0ldshadow\\libgenericwipe\\genericwipe.h"
int main()
{
	genericWipe("asd");
}

genericwipe.h

(Toggle Plain Text)

#ifndef GENERICWIPE_H
#define GENERICWIPE_H
#include "genericwipe.cpp"
bool genericWipe(const char *);
#endif

genericwipe.cpp

(Toggle Plain Text)

#include <windows.h>
#include <stdio.h>
#include <string.h>
bool genericWipe(const char *what)
{
    //note i removed the code here since its not important for this issue
    return true;
}

maybe its just me but i swear that this program shouldnt compile.. i thought that the genericwipe project would need to be compiled into a static link library and then the killer.cpp would need to add this static link library file to the linker... i have done none of this, yet the code compiles and works fine...

like i said before, i havent been coding in a while so maybe im just doing something blatantly stupid or whatever..

please note that this is issue no emergency but any advice would be great..
regards,--c0ldshadow

tempest · Sep 16th, 2005, 4:05 PM

I have no professional advice that i've gotten from books or anything, but my guess is that when a compiler sees a file in quotes on an include line it doesn't care what the extension is and just includes it as a header..

stevengs · Sep 16th, 2005, 4:23 PM

I would take a closer look at the following line in the genericWipe.h header file:

(Toggle Plain Text)

#include "genericwipe.cpp"

I would consider that at least a bit unorthodox.

Surely you see what is happening?

btw, good to see you around again mon ami.

EDIT: (ok, maybe I need to be more direct: try including "the other way around": include genericWipe.h in genericWipe.cpp.. get it now?

)

Ooble · Sep 16th, 2005, 4:23 PM

Can I suggest removing the path from your local #include?

stevengs · Sep 16th, 2005, 4:32 PM

Quote:

Originally Posted by Ooble

Can I suggest removing the path from your local #include?

Concrete paths, while less elegant and a true pain in the arse when the file structure changes, should not cause problems as long as they are correct. An abstract path would, however, definitely be preferrable.

(In German, we speak of concrete and abstract paths, what are the English counterparts? It doesn't sound quite right for some reason...)

Scorpions4ever · Sep 16th, 2005, 4:44 PM

This is where the problem is:

(Toggle Plain Text)

#include "genericwipe.cpp"

RULE #1: NEVER EVER #include C source. Here be hippogriffs and all that jazz. For one thing, it defeats the purpose of separate compilation, does useless compilation operations and It just invites too much grief (not to mention, duplicate symbol errors at link time with larger projects!).

Remove that line and instead, add genericwipe.cpp to your Makefile. Your new genericwipe.h should look like this:

(Toggle Plain Text)

#ifndef GENERICWIPE_H
#define GENERICWIPE_H

bool genericWipe(const char *);
#endif

The only things that should be in C header files are macros, defines and other preprocessor stuff, function prototypes, structs and typedefs and extern definitions. C++ headers may contain templated code, but that's it.

grumpy · Sep 16th, 2005, 4:51 PM

Quote:

Originally Posted by stevengs

(In German, we speak of concrete and abstract paths, what are the English counterparts? It doesn't sound quite right for some reason...)

If I understood your meaning, we speak of absolute and relative paths

stevengs · Sep 16th, 2005, 4:55 PM

Quote:

Originally Posted by Scorpions4ever

...The only things that should be in C header files are macros, defines and other preprocessor stuff, function prototypes, structs and typedefs and extern definitions. C++ headers may contain templated code, but that's it.

Yeah, that was what I was hinting at. coldShadow has programmed before, so I was kinda surprised. I tried to hint indirectly at first, but I guess breaking it over his head is cool too

. And reinforcing this point is never a bad thing. (and the #ifndef's to deter include loops are also all too often forgotten when a program is in it's tiny and insignificant beginnings... but then, when (not if!) the project grows, the beast rears it's terrible head and reveals it's horrid visage.

Thank you Grumpy, this particular gnawing at the back of my mind has ceased.

And, I must correct myself.. in German the 'pfad' it is also 'absolut' oder 'relativ'. In my defense, it is after midnight and it has been a difficult week

c0ldshadow · Sep 16th, 2005, 5:02 PM

wow. embarrassing mistake by me... i cannot believe i missed that lol. thanks for the advice. i havent been coding in a while and it shows.

peace,-c0ld

Scorpions4ever · Sep 16th, 2005, 5:11 PM

By the way, the ifndef's won't save you linking errors either. For instance:

(Toggle Plain Text)

genericwipe.h
============
#ifndef GENERIC_WIPE_H
#define GENERIC_WIPE_H

void genericwipe(char *);
#include "genericwipe.cpp"
#endif

main.cpp
========
#include "genericwipe.h"
int main(void) {
   ...
}


someotherfile.cpp
===============
#include "genericwipe.h"
int somefunc(void) {
   ...
}

Now, both cpp files include genericwipe.h, which in turn includes genericwipe.cpp. On compilation, both will compile fine, but when it comes time to link them all into a final executable, the linker will complain about duplicate symbol errors. Why? Because genericwipe.h included genericwipe.cpp and therefore, copies of all the code of genericwipe.cpp are now in main.obj as well as someotherfile.obj.

This is why you should never put source code (or variable declarations) in header files

.

Sep 16th, 2005, 4:05 PM	#2
tempest Programming Guru Join Date: Oct 2004 Posts: 1,041 Rep Power: 5	I have no professional advice that i've gotten from books or anything, but my guess is that when a compiler sees a file in quotes on an include line it doesn't care what the extension is and just includes it as a header.. __________________

Sep 16th, 2005, 4:23 PM	#3
stevengs Professional Programmer Join Date: May 2005 Location: Bad Nauheim, Germany Posts: 436 Rep Power: 4	I would take a closer look at the following line in the genericWipe.h header file: (Toggle Plain Text) #include "genericwipe.cpp" #include "genericwipe.cpp" I would consider that at least a bit unorthodox. Surely you see what is happening? btw, good to see you around again mon ami. EDIT: (ok, maybe I need to be more direct: try including "the other way around": include genericWipe.h in genericWipe.cpp.. get it now? ) __________________ -Steven "Is this a piece of your brain?" - Basil Fawlty

Sep 16th, 2005, 4:23 PM	#4
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Can I suggest removing the path from your local #include? __________________ Me :: You :: Them

Sep 16th, 2005, 4:44 PM	#6
Scorpions4ever Programmer Join Date: Jun 2005 Posts: 86 Rep Power: 4	This is where the problem is: (Toggle Plain Text) #include "genericwipe.cpp" #include "genericwipe.cpp" RULE #1: NEVER EVER #include C source. Here be hippogriffs and all that jazz. For one thing, it defeats the purpose of separate compilation, does useless compilation operations and It just invites too much grief (not to mention, duplicate symbol errors at link time with larger projects!). Remove that line and instead, add genericwipe.cpp to your Makefile. Your new genericwipe.h should look like this: (Toggle Plain Text) #ifndef GENERICWIPE_H #define GENERICWIPE_H bool genericWipe(const char ); #endif #ifndef GENERICWIPE_H #define GENERICWIPE_H bool genericWipe(const char ); #endif The only things that should be in C header files are macros, defines and other preprocessor stuff, function prototypes, structs and typedefs and extern definitions. C++ headers may contain templated code, but that's it.

Sep 16th, 2005, 5:02 PM	#9
c0ldshadow Unverified User Join Date: Jun 2005 Location: NJ Posts: 23 Rep Power: 0	wow. embarrassing mistake by me... i cannot believe i missed that lol. thanks for the advice. i havent been coding in a while and it shows. peace,-c0ld __________________ DeepTide The way is shut. It was made by those who are dead and the Dead keep it. The way is shut.

Sep 16th, 2005, 4:03 PM	#1
c0ldshadow Unverified User Join Date: Jun 2005 Location: NJ Posts: 23 Rep Power: 0	Program compiling even without reference to required static link files hey folks,i havent been doing that much programming over the last few months but ive gotten back into working on some stuff recently. basically the issue i'm having is that im getting a program to compile even though it shouldnt (at least i think). i have a libgenericwipe project that contains a .cpp,.h,and .dev file in it. this libgenericwipe has not even been compiled to generate any static link libraries. in a separate folder i have another project for the executable im making.. this project includes the .h file for libgenericwipe. in the linker section for this project, i am linking to nothing. the program compiles without any errors or linker errors and i am able to call the genericwipe function even without linking to anything.. my guess is im missing something very obvious or im just being stupid. here are the contents of my project files.. killer.cpp (Toggle Plain Text) #include <windows.h> #include "c:\\c0ldshadow\\libgenericwipe\\genericwipe.h" int main() { genericWipe("asd"); } #include <windows.h> #include "c:\\c0ldshadow\\libgenericwipe\\genericwipe.h" int main() { genericWipe("asd"); } genericwipe.h (Toggle Plain Text) #ifndef GENERICWIPE_H #define GENERICWIPE_H #include "genericwipe.cpp" bool genericWipe(const char ); #endif #ifndef GENERICWIPE_H #define GENERICWIPE_H #include "genericwipe.cpp" bool genericWipe(const char ); #endif genericwipe.cpp (Toggle Plain Text) #include <windows.h> #include <stdio.h> #include <string.h> bool genericWipe(const char what) { //note i removed the code here since its not important for this issue return true; } #include <windows.h> #include <stdio.h> #include <string.h> bool genericWipe(const char what) { //note i removed the code here since its not important for this issue return true; } maybe its just me but i swear that this program shouldnt compile.. i thought that the genericwipe project would need to be compiled into a static link library and then the killer.cpp would need to add this static link library file to the linker... i have done none of this, yet the code compiles and works fine... like i said before, i havent been coding in a while so maybe im just doing something blatantly stupid or whatever.. please note that this is issue no emergency but any advice would be great.. regards,--c0ldshadow __________________ DeepTide The way is shut. It was made by those who are dead and the Dead keep it. The way is shut.

Sep 16th, 2005, 5:11 PM	#10
Scorpions4ever Programmer Join Date: Jun 2005 Posts: 86 Rep Power: 4	By the way, the ifndef's won't save you linking errors either. For instance: (Toggle Plain Text) genericwipe.h ============ #ifndef GENERIC_WIPE_H #define GENERIC_WIPE_H void genericwipe(char ); #include "genericwipe.cpp" #endif main.cpp ======== #include "genericwipe.h" int main(void) { ... } someotherfile.cpp =============== #include "genericwipe.h" int somefunc(void) { ... } genericwipe.h ============ #ifndef GENERIC_WIPE_H #define GENERIC_WIPE_H void genericwipe(char ); #include "genericwipe.cpp" #endif main.cpp ======== #include "genericwipe.h" int main(void) { ... } someotherfile.cpp =============== #include "genericwipe.h" int somefunc(void) { ... } Now, both cpp files include genericwipe.h, which in turn includes genericwipe.cpp. On compilation, both will compile fine, but when it comes time to link them all into a final executable, the linker will complain about duplicate symbol errors. Why? Because genericwipe.h included genericwipe.cpp and therefore, copies of all the code of genericwipe.cpp are now in main.obj as well as someotherfile.obj. This is why you should never put source code (or variable declarations) in header files .

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Programming Forums > Application Development > C++

Program compiling even without reference to required static link files