What is weird about wrapping setjmp and longjmp?
- by Max
Hello. I am using setjmp and longjmp for the first time, and I ran across an issue that comes about when I wrap setjmp and longjmp. I boiled the code down to the following example:
#include <stdio.h>
#include <setjmp.h>
jmp_buf jb;
int mywrap_save()
{
int i = setjmp(jb);
return i;
}
int mywrap_call()
{
longjmp(jb, 1);
printf("this shouldn't appear\n");
}
void example_wrap()
{
if (mywrap_save() == 0){
printf("wrap: try block\n");
mywrap_call();
} else {
printf("wrap: catch block\n");
}
}
void example_non_wrap()
{
if (setjmp(jb) == 0){
printf("non_wrap: try block\n");
longjmp(jb, 1);
} else {
printf("non_wrap: catch block\n");
}
}
int main()
{
example_wrap();
example_non_wrap();
}
Initially I thought example_wrap() and example_non_wrap() would behave the same. However, the result of running the program (GCC 4.4, Linux):
wrap: try block
non_wrap: try block
non_wrap: catch block
If I trace the program in gdb, I see that even though mywrap_save() returns 1, the else branch after returning is oddly ignored. Can anyone explain what is going on?
