Wohoo, first post.
I have a problem with my code, the problem is that instead of writing "%" in res, when the pattern "%%" shows up, it writes it out as "%%" anyways. Currently I have it working so it works as strcpy. Seriously, I don't understand what I'm doing wrong. No matter what I do I can't make the loop process "%%". Here's the relevant code:
loop:
movb (%eax, %esi, 1), %cl # Move (*format[formati]) to %cl
testb %cl, %cl # (*format[formati]) == 0?
jz done # If yes, jump to done, else continue
testb %cl,prosent # (*format[formati]) == '%'?
je prosentloop # If yes, jump to prosentloop, else continue
# This byte isn't 0 and it isn't '%'
movb %cl, (%edx, %edi, 1) # *res[resi] = *format[formati]
incl %edi # resi++
incl %esi # formati++
jmp loop # Go through loop again
prosentloop:
incl %esi # Since % works more like a escape sign, we need to iterae
# formati to get the next charaxter
movb (%eax, %esi, 1), %cl # Moves next byte to %cl
testb %cl, %cl # (*format[formati]) == 0?
jz done # If yes, jump to done
testb %cl, prosent # (*format[formati]) == '%'?
je prosentcon # If it's a percent character again, jump to prosentcon
prosentcon:
movb %cl, (%edx, %edi, 1) # %cl is '%', store it at (*res[resi])
incl %edi # resi++
incl %esi # formati++
jmp loop # Jump back to loop
.data
prosent: .byte '%' # % - Percentage char is dec 37 and hex 25 in ASCII-table
Link to assembly file:
http://folk.uio.no/kabeern/sprinter.s
Link to C test file:
http://folk.uio.no/kabeern/test-sprinter.c 
Unsolved 
