Hi
The following code seems to be correctly executed when compiled with
GCC 4.4.7 and LLVM 6.1. It does not correctly compile with gcc version
5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4).
The following is what I have reduced the problem to:
#include <stdio.h>
#include <stdlib.h>
#define GENERAL 1
#define BRACKETS 2
#define QUOTES 3
//This method contains the issue.
void foo(char *qb, char* into) {
//The starting state is important for the bug.
int state = QUOTES;
int save_state = BRACKETS;
while (qb) { //Always true, it seems this can't just be '1'
printf("State is %d\n", state);
switch (state) {
case BRACKETS:
printf("Yay this was correctly executed\n");
exit(0);
break;
case GENERAL:
printf("Oh no how did you get here?\n");
printf("State is %d\n", state);
exit(1);
break;
case QUOTES:
state = save_state;
printf("State went to %d btw BRACKETS is %d\n", state, BRACKETS);
save_state = GENERAL; //Remove this line and it will work even
when optimised.
printf("After save state, state went to %d btw BRACKETS is
%d\n", state, BRACKETS);
break;
default: ;
}
printf("State %d btw GENERAL %d\n", state, GENERAL);
}
printf("If you see this then something is really wrong.\n");
exit(4);
}
int main() {
//These don't seem to matter don't concern yourself with them.
char *b = "123";
char out[4];
foo(b, out);
return 1;
}
If I compile this with:
gcc -O0 -g -Wall -Werror sillyswitch.c -o sillyswitch
It will correctly print "Yay this was correctly executed"
However if I compile this with:
gcc -O -g -Wall -Werror sillyswitch.c -o sillyswitch
It will print "Oh no how did you get here?"
I suspect this is a bug. I am unable to create an account to report
this as a bug though.
-Luke
