问题
I'm currently working with assembly language under the MIPS processor. I'm currently using MARS simulator and for reasons unknown I get the following error message after every run:
Go: running try.s
Error in : invalid program counter value: 0
Go: execution terminated with errors.
I get this error message independent of the code I'm using, just wondering if this is a bug in the MARS simulator or if it's something I'm missing.
回答1:
You probably finish your program with a jr $ra (return to caller). However, the code executed by MARS doesn't have a caller - it's executed at startup and has no function to return to, so the contents of $ra are zero.
The correct way to end a program on MARS is using the "exit" syscall:
li $v0, 10
syscall
回答2:
I am new to MIPS and I just had this problem. This is what I had:
.data
.text
swap:
# do stuff
jr $ra
main:
# do stuff
jal swap
li $v0,10
syscall
I fixed it by changing it to this:
.data
.text
main:
# do stuff
jal swap
li $v0,10
syscall
swap:
# do stuff
jr $ra
Notice I moved main to be before swap. I mistakenly assumed that main was a reserved label. And that it would automatically jump straight to main first. But apparently that isn't the case because it was hitting my jr $ra instruction before I got to call jal swap in main.
Anyway, I hope this helps.
回答3:
I know this question is old, but for anyone who was just like me and was desperately Googling for an answer: try doing the above syscall thing instead of a return, and try putting your main function before all other labels. Also, there's a "Initialize Program Counter to global "main" if defined" under the Settings menu; make sure that is checked. I do not know if enabling that allows you to put your main label after other labels, as I haven't tried that yet. What I have described is what I did to make it work, and nothing else. Good luck!
来源：https://stackoverflow.com/questions/2826935/invalid-program-counter-value-0