问题描述
我无法弄清楚如何在中缀表达式中添加空格，以便像 3+5 这样的东西变成 3 +5。我不断收到分段错误，我什至无法确定错误来自哪一行，因为出于某种原因，我也无法打印出任何内容。这是我的代码供参考：
.data
.balign 4
return: .word 0
.balign 4
operations: .asciz "+-*/^"
.balign 4
output: .space 100
.balign 4
spa: .asciz " "
.text
.global printf
.global main
main:
ldr r0,[r1,#4] //load address of first character in expression
ldr r1,=return
str lr,[r1] //store lr in return variable
ldr r2,=output //load address of output on r2
ldr r3,=spa //load address of space variable
ldr r3,[r3] //load character ' ' onto r3
loop:
cmp r0,#0 //check if reached end of input
beq end //if so go to end
ldr r1,=operations //load the address of operations string in r1
loop2:;
cmp r1,#0 //check if reached end of operation string
beq loop3 //means the current character in output isn't an operator
ldr r5,[r1] //else load value of r1 in r5,the current operator
ldr r6,[r0] //load current value in input string to r6
cmp r5,r6 //compare the two values
beq loop3 //if equal go to loop3
add r1,r1,#1 //if not increment address of r1
b loop2 //start next iteration of loop2
loop3:
str r3,[r2] //since current character is an operator,store space first
add r2,r2,#1
b loop4 //on output string. Then go to loop4
loop4:
str r6,[r2] //store the current character,stored in r6,in r2
add r0,r0,#1 //increment address of r0 by 1 to get to next character
add r2,#1 //increment address of r2 by one to get to next slot in array
b loop //start next iteration of loop
end:
ldr r0,=output //load address of output onto r0
bl printf //print out string
ldr lr,=return //restore link register
ldr lr,[lr]
bx lr
解决方法
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