Well, this is a homework question, but I need help!

What I need to do is to read 1024 bytes from "filename.txt" using fopen, fread, and fclose using ASM.

in C:

#include <stdio.h>
int main() {
  char buffer[1024];
  FILE* file = fopen("filename.txt","r");
  fread(file,buffer,1024);
  fclose(file);
}

Sure, I can use -S and take a look to the .s but it's very difficult to read... (for me)

So, these are my ideas (ASM):

I know it sucks, but anyone can help me?

I havent used x86 asm in a while, but I dont think you can just push strings onto the stack. You have to have a data section or something and give them labels, then move the labels into registers and push the registers onto the stack. For easy reference on how to do this, just use gcc -S

yes is true.
The -S flag include a lot of stuff and "advanced asm" I don't understand it

C functions are prepended with a '_', so the correct function names are _fopen, _fread and _fclose.

[edit]
You can't push strings or characters into the stack. You have to create a string in the data segment with the string contents and push the address.

Ok, if I change the string stuff, this is a good sketch?

Not necesarilly. They aren't in Linux, but they are in some versions of MinGW.

The xor is useless, you don't want to set eax to 0 for anything.

Funaction arguments are pushed in reverse order, from right to left.

Remove the pop after the call to fopen.

I don't know what offset and length are. I've never seen them.

But if it's homework... what is your teacher doing? Not teaching you, certainly

They're in all versions of MingW I've tryed. Also in MSVC and in the old TurboC. I though that was part of the standard. I don't know why this is not true in linux.

Same here, but APEG prepends its asm functions with _ in MinGW and the C code refuses to recognize them for some people. Even removing the _ apparently doesn't do anything. :/

As for the xor, I see a lot of assembly code do that to set a register to 0. I just assumed it was more CPU efficient.

Yes, xoring is faster than a 'mov eax, 0', but he doesn't need to set eax to 0 in the first place

[edit]
One more thing. This may depend on the assembler you use, but I think the keyword for importing symbols is 'public', not 'extern'.

cookies!

okay, then, the code approximated is this: ?

// When use the buffer??

Lukas

You've created a 2nd account?

The return value is stored in eax, not in the stack. So fopen will put FILE* in eax.

Have you tried that code and see if it works? I think that would be much easier.

You should also check eax is different from NULL after opening the file.

No, he's a friend (lukas) Im lucaz.
We'll fix the pops.

I'll try the code now.

EDIT:
welcome back reybrujo!, donde estabas?

Got a user interface course on the last week of January, and then spent most of February doing interface testings and user testings. I missed the hardcore of C programming, though

Its the object file format. elf doesn't require it, but PE/COFF does.

BTW, you can push strings on the stack. You just can't use them like that. You have to pass esp as the argument to the function, since the function wants a pointer.

Thanks, I get a 7