Lab 3 - IDA

Reference counting
“poor man's garbage collector”
• Parent – Child needs a new data structure
• Who will free this memory depends on who exits last
• Many ways to implement this. Suggestion: you can use
reference counting:
– struct child_status{
int exit_status;
/* ... */
int ref_cnt;
};
child
– /* Initialize it */
struct child_status * cs = malloc ... ;
cs­>ref_cnt = 2; /* both parent and child live */
cs
parent
– /* When parent or child is done with cs: */
cs­>ref_cnt­­; /* Needs to be protected by a lock */
if ( cs­>ref_cnt == 0 ){ free( cs ); }
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