Reputation: 111
Full disclosure the following code is for a homework, but I wrote the code I just need help figuring out why I'm getting several errors when trying to compile it (My professor never talked about GCC errors).
I wrote a function that returns the sum of the two largest members of an array of size 10. I've marked the lines 70 and 74:
function1:
pushl %ebp
pushl %ebx
movl $2, %ebx #ebx will be counter
movl %esp, %ebp #first will be %edx and second will be %eax
movl 8(%ebp), %edx #first = arr[0]
movl (%edx,1,4), %eax #second = arr[1] **LINE 70**
cmpl %eax, %edx #if(arr[0] > arr[1]) don't jump
jle .L6
.L7:
movl (8(%ebp),%ebx,4), %ecx #%ecx = next value to compare **LINE 74**
cmpl %ecx, %edx #if first > next don't jump
jle .L8
cmpl %ecx, %eax #if second > next don't jump
jle .L9
cmpl $9, %ebx #check if counter = 9
je .L10
addl $1, %ebx #counter++
jmp .L7
.L6:
movl %edx, %ecx #move arr[0] into %ecx
movl %eax, %edx #first = arr[1]
movl %ecx, %eax #second = arr[0]
jmp .L7
.L8:
movl %edx, %eax #move previous first into second
movl %ecx, %edx #move new first into first
addl $1, %ebx #counter++
jmp .L7
.L9:
movl %ecx, %eax #move new second into second
addl $1, %ebx #counter++
jmp .L7
.L10:
addl %edx, %eax
popl %ebx
popl %ebp
ret
I am getting the following error messages:
assign3.s:70: Error: expecting `)' after scale factor in `(%edx,1,4)'
assign3.s:74: Error: missing ')'
assign3.s:74: Error: missing ')'
assign3.s:74: Error: junk `(%ebp),%ebx,4))' after expression
I appreciate the help and let me know how I can improve my questions in the future
Upvotes: 1
Views: 1189
Reputation: 111
I had to rework my code completely but thanks to @fuz I was able to find the proper solution. My problem was both in syntax and in understanding of registers and pointers. Here's the correct code:
function1:
#FIRST %edx
#SECOND %eax
#THIRD %ebx
#LOCATION OF ARRAY %esi
#COUNTER %edi
pushl %ebp
pushl %ebx
pushl %esi
pushl %edi
movl %esp, %ebp
movl $1, %edi
movl %eax, %esi
movl (%esi), %edx
movl (%esi, %edi, 4), %eax
addl $1, %edi
cmpl %eax, %edx
jle .L6
.L7:
movl (%esi, %edi, 4), %ebx
cmpl %ebx, %edx
jle .L8
cmpl %ebx, %eax
jle .L9
.L11:
addl $1, %edi
cmpl $10, %edi
jne .L7
jmp .L10
.L6: #Switch FIRST and SECOND
movl %edx, %ebx
movl %eax, %edx
movl %ebx, %eax
.L8: #THIRD is bigger than FIRST
movl %edx, %eax
movl %ebx, %edx
jmp .L11
.L9: #THIRD is bigger than SECOND
movl %ebx, %eax
jmp .L11
.L10: #Add and return
addl %edx, %eax
popl %edi
popl %esi
popl %ebx
popl %ebp
ret
Upvotes: 1