C++: Fix false positive in PointlessComparison #1236
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We avoid putting a variable into SSA if its address is ever taken in a way that could allow mutation of the variable via indirection. We currently just look to see if the address is either "pointer to non-const" or "reference to non-const". However, if the address was cast to an integral type (e.g. `uintptr_t n = (uintptr_t)&x;`), we were treating it as unescaped. This change makes the conservative assumption that casting a pointer to an integer may result in the pointed-to value being modified later. This fixes a customer-reported false positive (#2 from https://discuss.lgtm.com/t/2-false-positives-in-c-for-comparison-is-always-same/1943)
jbj
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Apr 11, 2019
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jbj
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LGTM. I agree this is the right place to add this logic.
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We avoid putting a variable into SSA if its address is ever taken in a way that could allow mutation of the variable via indirection. We currently just look to see if the address is either "pointer to non-const" or "reference to non-const". However, if the address was cast to an integral type (e.g.
uintptr_t n = (uintptr_t)&x;), we were treating it as unescaped. This change makes the conservative assumption that casting a pointer to an integer may result in the pointed-to value being modified later.This fixes a customer-reported false positive (#2 from https://discuss.lgtm.com/t/2-false-positives-in-c-for-comparison-is-always-same/1943)