Make contract of free (for C) conditional on ptr being non-null #1250
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In C, passing NULL to `free` has no effect. This change weakens the
precondition on the argument to `free` so that it only applies if the
pointer is non-null, so this program now verifies:
#include <stdlib.h>
int main(){
int* xs = NULL;
free(xs);
free(xs);
free(xs);
}
Adds test; changes existing test; fixes utwente-fmt#1240.
superaxander
approved these changes
Sep 27, 2024
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In C, passing NULL to
freehas no effect. This change weakens the precondition on the argument tofreeso that it only applies if the pointer is non-null, so this program now verifies:Adds test; changes existing test; fixes #1240. As @bobismijnnaam mentioned in that issue, this does introduce a number of branches - the hope there was that this "would not influence verification significantly", but I'm not sure how to check this; the existing examples seem to be okay, but those are quite small.