Ok, with an actual sample of code that broke it was easy to fix. The bug was not in the optimization rule itself, which was sound, but in the dependency analyser. It didn't check arguments to side-effect free functions for written variables. Fixed in Pike 7.0, 7.2, 7.4 and 7.5.
/ Henrik Grubbström (Lysator)
Previous text:
2003-03-20 10:26: Subject: for-loop optimization
I just wrote a for-loop like this:
string foo="gazonk";
for(int i=0;i<sizeof(foo);i++) {
... do stuff ...
if (sometimes) foo = foo[1..];
... do stuff ...
}
The problem I discoverd was that when the length of foo is changed, the loop still tries to loop over the original length of foo. The problem dissappeard when I replace sizeof(foo) with a variable and update it when changing the length of foo.
Is this the correct behaviour or is the optimizer doing more than it should here?
/ Marcus Agehall (Trådlös)