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hi!
i need to have some static variables in one file. this file and another one have to access them. but whereever i put the static variable declaration in, the other file can not read it. not even when i include it's header file.
i'm only including the cpp's header files. the static declarations are within the cpp file.
thanks for reading and helping :)
So if you have a variable declared static outside of a function, then you're telling the compiler that no other file can see it.Quote:
Originally Posted by MSDN
So, don't declare it static. Details are a little fuzzy, but I'm guessing you need to make one of your declarations extern.
extern - what does that mean?
in my structure, main.cpp includes engine.h and engine.h includes utility.h
in utility.h AND in engine.h i need those static variables.
where can i define them? (i may not define them in main.cpp)
static variables at file scope are not linked to variables in other translation units (read: files), so yeah, it wouldn't be the same variable.
What are you trying to do?
edit: define your variables in the source files, and put the extern declarations in the header files.
http://www.cprogramming.com/tutorial/statickeyword.html
http://faq.cprogramming.com/cgi-bin/...&id=1043284392
i'm trying to use those static variables in engine.cpp AND utility.cpp
Static variables inside functions cannot be accessed outside the function, whatever you do. Global variables do not need to be static since they will retain their value until the end of the program, so specifying static to a global variable if you want a static-type global variable is wrong.
So it comes down to the question of what you're trying to do, since the only other solution would be global variables which is to be avoided.
Isn't it possible, for example, somehow to pass those variables as arguments to a function?
nope. it isnt.
but maybee i have to define them before engine.cpp includes utility.h
edit: nope, is not-good
btw: i'm declaring those static variables in engine.cpp outside of any function and after i included utility.h
Explain your situation! Maybe show some code of how it's used and done.
hm maybee i can post parts of the long code:
main.cpp:engine.cpp:Quote:
#include "engine.h"
utility.cpp:Quote:
#include "utility.h"
.....
.....
.....
_____STATIC VARIABLES IN USE HERE____
Quote:
#include "engine.h"
static _____SOME VARIABLES HERE_____
......
......
......
_____STATIC VARIABLES IN USE HERE____
Yes, so how are the internal linkage global variables used?
what variables? do you mean my static floats i declared in utility.h?
they are declared there and used in both files.
but where ever i include these variables, the other file can not access it...
Your utility.cpp "static" variables which are actually internal linkage global variables.
How are they used in your headers?
>i'm trying to use those static variables in engine.cpp AND utility.cpp
You can't use a static global variable in two files. You just can't. static has a different meaning when applied to variables in file scope, like a global variable, than to variables in a function, which have local scope.
static in a variable in file scope (read: not in a function or a struct) is only linked in that file. If you try to use that variable in another file, you will get a undeclared identifier error.
If you declare another variable in another file with the same name as your static variable, it will be another variable, with another memory location.
The only way you could get a static variable in two source files to refer to the same variable is if you included one file in the other.
i included engine into utility and utility into engine.
thats what you told me. and it doesnt work either :(
Come on, work with us here! How do you use your said variables? Code, please!
I didn't mean that you should actually do that.Quote:
Originally Posted by Devils Child
Try removing the static keyword.
ok.
http://www.dev-ch.de/upload/files/De...lGL2_Demo2.zip (831.67 KB)
here is the complete source code. you might not be able to compile and run it, but the principe is clear.
the variables that are static are declared in matrix.cpp and want to be used in virtualGL.cpp
i hope you understand the code as it is, it is very long you know...
edit: removing the static keyword does not make a difference
If you want to use those variables in another source code file, you must not declare them static in matrix.cpp. Declare them normally in matrix.cpp, and use the "extern" keyword in virtualGL.cpp.
Having said that, you really really really really really really want to make that matrix a structure, and maybe turn some other things into structures and classes as well. Doing so will (1) make all your computations much easier, and (2) allow you to have more than one matrix at any given time, and (3) make writing code much easier, since you can use somewhat-more-normal syntax. (For instance, look at vgliTriangleFill: instead of fifteen input parameters, you could pass in 3 Point objects, or better yet a vector/array of Points, and then all those nearly-identical lines of code could be done with a for-loop, and all those swaps could just be swap_Points, etc.)
i was thinking of putting it into a class later, but while we are at this right now: i tried once to build up a texture class, but that gave EXACTLY;) the same problem: i had problems with the declarations, so:
1. (how) do i have to declare a class in the header file?
2. when this is done, i should be able to access this class from _every_ cpp file that is included there.
/* the thing with the triangle fill routine: hm i think it's a lot easyer and a bit of my style ;) since in c++ you can wrap lines between tokens this is giving me the oppertunity to do more than 20 parameters to a function LOL */
You'll need to put the class definition in an included header file, yes.
Objects are just variables, but of a fancier type (instead of int i, you have Point i); so the same scoping rules apply: static variables are only visible in the file in which they are declared; extern variables are defined elsewhere and used in this file, etc.
yeh, i know how to use classes but i dont know how to declare them in the header files *shame* ;)
and when i write extern instead of static i get the same error :(
I don't see where the global variable is used nor defined.
Can you explain where?
Also, I suggest you avoid this:
Do it the right way:Code:void swap_int(int* x, int* y) {
int temp;
temp = *(int*)x;
*(int*)x = *(int*)y;
*(int*)y = temp;
} void swap_int64(__int64* x, __int64* y) {
Code:void swap_int(int* x, int* y) {
int temp;
temp = *(int*)x;
*(int*)x = *(int*)y;
*(int*)y = temp;
}
void swap_int64(__int64* x, __int64* y) {
Perhaps a stupid (as in does-nothing), yet illustrative, example is in order:
point.h:
point1.cpp:Code:class Point {
double x, y, z;
}
point2.cpp:Code:#include "point.h"
Point a, b, c; //global variables -- bad practice, but we're illustrating
static Point d, e, f; //complete opposite of global variables -- can never be seen in point2, no matter how hard you try
Code:#include "point.h"
extern Point a, b, c; //same variables as in point1, through the magic of linking
// if we don't link the object file point1.o, we're in trouble
tabstop: your explanation works! i just have to declare them not static in the main file and extern in all other files. also it is a lil bit messy to declare all those values as extern in the other files, but well...
(elysia: i do that messy thingy only because these swap functions only differs by their datatypes)
so now the only question left is, how to do the same thing wth classes.
i will declare a class in the virtualGL.cpp and want to use it in other files, too,...
As messy as static?Quote:
Originally Posted by Devils Child
And if you have a lot of functions that differ only in their prototypes, then why don't you use templates?
Um ... that was a class? I don't know what you mean by "declare a class"; if you mean write out code or whatever, you need to have the class definition (the bit that that's in the header file here, plus function prototypes) in a header file, no matter what anyway. You can then write out the actual functions in a .cpp file.Quote:
so now the only question left is, how to do the same thing wth classes.
i will declare a class in the virtualGL.cpp and want to use it in other files, too,...
What's with the casts?Quote:
Code:void swap_int(int* x, int* y) {
int temp;
temp = *(int*)x;
*(int*)x = *(int*)y;
*(int*)y = temp;
}
And why not just use what's already there?
Code:using std::swap;
swap(x, y);
hm that swap command really exists :P
i replaced my one with that one;)
now to the classes: all i need to do is write the class declaration including its' functions into the header file and all other files are able to use that class? (cause that ain't working ..:()
No, you define the class in the header and implement the functions in a .cpp file (unless it's a template function or template class).
But this still probably leaves the problem that you're going to make global objects. I can just hope you won't do that.
Then include the header and it will magically work.
well, it magically gives me a stack overflowCode:class vglTex {
private:
public:
int w, h, buf[513][513];
/*void LoadFromFile(char path[]) {
SDL_Surface* image = SDL_LoadBMP(path);
w = (*image).w;
h = (*image).h;
for (int x = 0; x <= w; x++) {
for (int y = 0; y <= h; y++) {
buf[x][y] = GetPixel(image, x, y);
}
}
SDL_FreeSurface(image);
}*/
};
'Cause 512 x 513 x 4 = 1 052 676 (~1 MB). Stack overflow.
Allocate buffer on heap.
Sheesh.
This is not necessary.Code:w = (*image).w;
Will do just fine.Code:w = image->w;
why would that cause a stack overflow? - i mean, i need some bytes to store the texture. accessing the texture via the image would be slow....
so what else should i use instead of an array?
and what's about the class problem? :P
Well, the stack is limited to about 2MB, so if you create a local variable of 1MB+, you have already used up half the stack in one fell swoop. Better to use a heap-allocation (new), and free it after use (delete).
--
Mats
VC++ sets stack to 1 MB by default. You could increase this, but it's better to allocate on the heap (new/delete).
whats that? is that a kind of array that is as fast as one?
because i need to store the texture in some sort of array.
in basic it would beCode:CreateBank()
FreeBank()
PokeInt(...)
PeekInt(...)
Oh gods. You don't even know about the heap? :rolleyes:
http://www.cprogramming.com/tutorial...eory/heap.html
http://www.cprogramming.com/tutorial/lesson6.html
Long story short (KISS), the stack is the stack and the heap is the computer RAM.
you can use vector instead of array. It will allocate memory dynamically and handle it for you
hm ok. this seems better than an array.
but there is still one question open: how do i do that thing with the classes?
you said that i need to define the class in the virtualGL.h file and write it's functions to virtualGL.cpp
but then the compiler says something like "___CLASS_NAME___ is not a class"
umh...
Show the code, then.
i did show the code here lately, but i will upload it again with the class :)
http://www.dev-ch.de/upload/files/De...lGL2_Demo3.zip (1.64 MB)
the class is called "vglTex" and is my texture class. if i get how it works, i will implement a matrix and a program class.
You only really need to show the code for the class...
Well, it's defined in VirtualGL.h, so include VirtualGL.h in appropriate source files.
And don't implement the functions in the header -_- Though we told you to do it in the source file.
this code how it is gives me this error log:and you just told me that it would work.Code:1>------ Build started: Project: VirtualGL, Configuration: Debug Win32 ------
1>Compiling...
1>Matrix.cpp
1>d:\martin\progs\c++\virtualgl\vgl-inc\virtualgl.h(6) : error C2065: 'SDL_Surface' : undeclared identifier
1>d:\martin\progs\c++\virtualgl\vgl-inc\virtualgl.h(6) : error C2065: 'image' : undeclared identifier
1>d:\martin\progs\c++\virtualgl\vgl-inc\virtualgl.h(6) : error C3861: 'SDL_LoadBMP': identifier not found
1>d:\martin\progs\c++\virtualgl\vgl-inc\virtualgl.h(7) : error C2227: left of '->w' must point to class/struct/union/generic type
1> type is ''unknown-type''
1>d:\martin\progs\c++\virtualgl\vgl-inc\virtualgl.h(8) : error C2227: left of '->h' must point to class/struct/union/generic type
1> type is ''unknown-type''
1>d:\martin\progs\c++\virtualgl\vgl-inc\virtualgl.h(11) : error C3861: 'GetPixel': identifier not found
1>d:\martin\progs\c++\virtualgl\vgl-inc\virtualgl.h(14) : error C3861: 'SDL_FreeSurface': identifier not found
1>Sample.cpp
1>d:\martin\progs\c++\virtualgl\vgl-inc\virtualgl.h(11) : error C3861: 'GetPixel': identifier not found
1>d:\martin\progs\c++\virtualgl\vgl-inc\utility.h(2) : error C2365: 'GetPixel' : redefinition; previous definition was 'formerly unknown identifier'
1>Generating Code...
1>Build log was saved at "file://d:\Martin\Progs\C++\VirtualGL\Debug\BuildLog.htm"
1>VirtualGL - 9 error(s), 0 warning(s)
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
to the headers: i always thought that the function should be declared in the header file? or what else would it be good for??
anyway, how do i finally get this class working in every cpp file?
It does work. You're just not doing it right. The header VirtualGL.h obviously needs to include other heads, specifically the SDL headers that contains the SDL_Surface header.
It's very, very easy:
Code:// Definition in .h file
class CFoo
{
public:
void foo(int foo);
};
// Implementation - .cpp file.
void CFoo::foo(int foo)
{
// My code
}
oki :) now it's finaly working!
great job guys! thanks a lot :)
oh wait! when i declare an object of the class vglTex like this:, the compiler tells meCode:vglTex tex;
what does that mean?Quote:
syntax error : missing ';' before identifier 'tex'
Usually means the compiler doesn't know what vglText is, so it thinks there must a ; after it.
Which in essence means you haven't shown the compiler the class (or type) definition, which probably means you've probably not included the correct header.
Most likely, the compiler doesn't know what the type vglTex is - you need to include the appropriate header file for that class.
--
Mats
i wanna define that object in vurtialGL.cpp and the class is defined in virtualGL.h
i dont include that file, because it is automaticly included isnt it?
well you see the source code i uploaded lately (..._demo3.zip)
what is it that i'm doing wrong? i think i might mis understood the usage of header files as well as several other mistakes... tell me please :)
No, there are no "automatically included" header files - anywhere.
--
Mats
The best thing to do is break classes into their own source files/headers so you can freely include those headers anywhere.
these include issues are so over complicated... what exactly does every of these 7 files include?
Includes are not complicated. You must simply include a file that contains a declaration of definition of what you're trying to use.
So make a vglTex.cpp file to contain the implementation. The source file should include vglTex.h, which contains the class definition, and all files that uses the class vglTex should also include vglTex.h.
dont know what i am doing wrong but it sure is my fault: i mean, i'm not very sure about all this. this works well, but as soon as i need classes, everything stops working well...
sample.cppvirtualGL.cppCode:#include <string>
#include "SDL/SDL.h"
#include "VGL-Inc/VirtualGL.h"
#include "VGL-Inc/Matrix.h"
#include "VGL-Inc/Utility.h"
virtualGL.hCode:#include <string>
#include <time.h>
#include "SDL/SDL.h"
#include "Matrix.h"
#include "Utility.h"
matrix.cppCode:#include "SDL/SDL.h"
#include "Utility.h"
matrix.hCode:#include "VirtualGL.h"
utility.cppCode://
utility.hCode:#include "SDL/SDL.h"
Code://nothing included here
To rule out circular dependencies, you can try to break it out into its own source file/header as I mentioned.
I don't know where the class is used (and I believe it's defined in VirtualGL.h).
yes it is.
anyhow... what do you want me to do now that you see my include structure?
Split the class into its own files.
If you include the correct header and it still isn't working, then either your compiler is broken (unlikely) or you have circular dependencies - ie file A includes file B and file B includes file A.
Plus if you split it, it will much easier to debug what it isn't working if it's not working.
hey cool man:)
it's working when i use an external header file for the class :)
thanks again ;)
i'll be here when something doesnt work again and i dont get it.
oh there is another tricky problem (sorry):
VirtualGL.cpp:Classes.h:Code:vglTexture *vglTextur;
of course the vglTexture variable is not defined at this point, but it can not be defined there because the class doesnt even exist yet...Code:class vglTexture {
private:
public:
int w, h, buf[257][257];
void LoadFromFile(char path[]) {
SDL_Surface *image = SDL_LoadBMP(path);
w = image->w;
h = image->h;
if (w > 256) w = 256;
if (h > 256) h = 256;
for (int y = 0; y <= h; y++) {
for (int x = 0; x <= w; x++) {
buf[x][y] = GetPixel(image, x, y);
}
}
SDL_FreeSurface(image);
}
void SetActive() {
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
vglTextur = this;
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
}
};
i guess there is a pretty easy solution for this umh...
This is very bad programming. Do not use global variables and using a class to set an active global pointer is just another bad programming step.
Objects are self-contained. They do all the necessary work to function and expose interfaces for the programmer to work with them. There shouldn't be a SetActive function to set a global pointer to this class there.
Each function that works with such a class should instead take an argument to a vglTexture object, and not use a global "active" pointer.
And I stressed this before, implement the functions in the source file, not the header.
sure it is bad programming, but how does the program know which texture is the active one?
you mean that i should add a parameter to the texture class such as "bool active;" ? how would that work? i dont even know how to iterate trough classes :(
By doing something like "ActiveTexture = SomeTexture;"
Most graphics environments have a "Graphics Context", which is some sort of object/structure that contains "everything current" (or active to use your term). There are calls to "SetActiveXXXX", where XXX may be texture, pen/brush, etc, etc.
--
Mats
Of course, I don't know how the program looks, but something like a graphics context and a few things like active textures might be global, but the class itself should certainly not set it.
When using global variables, don't forget to use const-correctness.
what?
edit: ah i shell use an external function to set the active. why didnt i came to this idee *lol* :D
You can use an object to keep track of your graphics context. You could make it global.
The class for this should have pointers for the active texture, for example and you can set/get it with appropriate functions in the class itself.
This or something in lines with it what I believe mats is suggesting.
Yes, I agree with Elysia - one, perhaps global, graphics context that "ties everything else up" is the common way to do graphics implementations.
--
Mats
thats what i tried and it caused several errors:
Code:// Somewhere in the example:
vglTexture tex;
tex.LoadFromFile("Media/Texture2.bmp");
vglBindTexture(tex);
// Declaration of vglTextur:
vglTexture *vglTextur;
// Somewhere in the code:
void vglBindTexture(vglTexture tex) {
vglTextur = &tex;
}
What do you this code does? It makes a copy of your texture and then assigns the address of it to a global pointer. But when the function exits, that copy is gone. Destroyed. Oops.
Suggest you try what was outlined above.
i'm a newbee and i dont understand it :(:(:(
The incoming variable of "tex" in vglBindTexture() is a local copy of the object. Then you assign a global variable with the address of this variable, and leave the function - the local copy no longer exist.
You can fix it by making the vglBindTexture take a pointer, and pass the address of your texture.
--
Mats
You have no idea what passing by-value, by-pointer or by-reference is and you didn't know how to make a class and you're playing around with graphics and classes?
I think you need to go back and try to learn a little more basics.
Without proper basics, you won't get far.