visual c++ for-loop problem

[hojjatrakhshani]

hi guys !
problem is print charachter on screen
with loop it isnt work?
without loop its work?

for-loop:

Code: Select all

void __cdecl write_string(char colour, const char *string )
{
    volatile char *video = (volatile char*)0xB8000;
    for(int x=0;x<17;x++)
    {
        *video++ = *string++;
        *video++ = colour;
    }
}

no for-loop

Code: Select all

void __cdecl write_string(char colour, const char *string )
{
        volatile char *video = (volatile char*)0xB8000;
        *video++ = *string++;
        *video++ = colour;
        *video++ = *string++;
        *video++ = colour;
         etc......
}

[gerryg400]

Neither of them has printed 17 characters. So I would say that both are wrong.

[hojjatrakhshani]

suppose correct picture print either 17 charachter?

[gerryg400]

I'm sorry but I don't understand your post.

[Gigasoft]

Check that ESP points to RAM.

[Nable]

What about looking at disassembly?

[hojjatrakhshani]

hi!
i look at main.asm it is correct?
y can see

[bluemoon]

As Gigasoft mentioned, it sound like a stack issue.
I do not see any startup code in kmain except setting ds/es/fs/gs, so are the proper environment setup on the boot loader? C code depends on some conditions - you should know that.

[hojjatrakhshani]

i set it but...

Code: Select all

	_asm {
		cli
		mov ax,0x10
		mov ds, ax
		mov es, ax
		mov fs, ax
		mov gs, ax
             	mov	ss, ax
		mov	esp,0x90000
	}

[AndrewBuckley]

You will want to set up stack before you enter your C code, using a _asm block inside of C to do that will just be a headache, if possible at all.

[Tosi]

Did you read the Required Knowledge and getting started articles on the wiki?
You seem to have no idea what you are doing.

[hojjatrakhshani]

thank!i am set them either from my boot loader when it is go to protected mode.
but you can set them in your c code entry point,there is problem?
sorry i am not set base address?