Re: [Dev-C++] gas again

[<cg...@wo...>]

Jaaaaaa!!!!!!
I achieved to do it right!!!!
The correct code, with comments, for those who could be interested in=20
the subject:

/*Veamos c=F3mo se ensambla esto*/
#.include "asm_io.S"

.data
mensaje4: .ascii "Introduzca un n=FAmero\n\0" # Template strings for
                                                                  #=20
printf and scanf
mensaje5: .ascii "El doble es: \0"
string1: .ascii "%d\n\0"
string2: .ascii "%d\0"
string3: .ascii "%s\0"   =20
string4: .ascii "%s\n\0"
string5: .ascii "%c\n\0"
numer: .long 1    #I've not achieved to use this variable yet
                         # I only can output it, but not input a value
                         # from stdin

.bss
.comm entero, 4 # Here I'll put an integer number from stdin
                          # using scanf, then I'll sum it by itself and=20
output
                          # the result
.comm string, 255  # A string, I'll input a phrase and output it
                             # and the second character from it.


.text
numer =3D 200 #I set numer to be =3D 200,  without this line
                     # it is not =3D!, but to whatever value
#entero =3D 100  ##if I add this line, then I get an
                       ## error when input.
.global _asm_main
.extern _printf
.extern scanf # I forgot the underscore, but it works
_asm_main:
enter    $0, $0
pusha

movl $mensaje4, %eax
pushl %eax
call _printf
addl $4, %esp # I changed the number added to %esp

movl $entero, %ebx # I pass the variable
                               # If I pass numer here
                               # I have use the template
                               # "%l" for printf
pushl %ebx
movl $string2, %eax # "%d"
pushl %eax
call _scanf
addl $8, %esp

movl entero(,1), %eax # I pass the direction of entero
                                   # With numer, I use $numer
                                   # and it is accepted (with numer(,1)
                                   # it generates an error and
                                   # is closed by windows
                                   # But its value is still 200, not the
                                   # new input from stdin.
pushl %eax
movl $string1, %eax # "%d"
push %eax
call _printf
addl $8, %esp

movl entero(,1), %eax
addl %eax, %eax # sum it by itself
pushl %eax # And print the result
                  # But I don't store it
                  # back to the variable
movl $string1, %eax
pushl %eax
call _printf
addl $8, %esp

mov $string, %ebx # I pass the string variable
push %ebx
movl $string3, %eax
push %eax
call _scanf # And read from stdin
addl $8, %esp

movl $string, %eax
push %eax
movl $string4, %eax
push %eax
call _printf # I display the whole string
                 # If you use a string with whitespaces
                 # you'll see that, as C, it's printed only
                 # till the last char before the space
                 # And that's what where stored in the
                 # string variable from input
addl $8, %esp

movl $1, %ebx # I pass the index I want to %ebx
mov string(,%ebx,1), %ecx # I pass to %ecx the
                                          # value which in C would
                                          # be denoted by string[1]
push %ecx
movl $string5, %eax # "%c\n\0"
push %eax
call _printf # I print the second char of string
addl $8, %esp

popa
movl    $0,    %eax
leave
ret


Regarding the objection by Per Westernak (Thank you!)  You were right,=20
it worked fine till I used the last paragraph of code, there I had added=20
so many to %esp it returned access violation, I changed the numbers,=20
assuming that the functions printf and scanf had done yet the removal of=20
the returning address and restored and popped out its %ebp (Which is the=20
correct, %ebp is restored an popped out explicitly by the callee and the=20
return address is popped implicitly by ret, just as it was implicitly=20
pushed with call. I forgot this).