Previously, we would try to find an element enclosing each macro
access. This is not in general well-defined, especially in the
context of template instantiations -- macros are a lexing-time
concept, and don't map cleanly onto AST elements.
The check that an instruction is in the same function as its operands is
hopefully redundant and can be removed. Just to be sure, I've added the
check to a sanity query.
This check turned out to cause bad performance in the alias analysis
because it got inlined into `AliasAnalysis::resultEscapes` and then
pulled out to a loop-invariant predicate that got a bad join order. With
this check removed, the `ssa/AliasAnalysis.qll` file is orders of
magnitude faster.
This follows what's been done for JavaScript. The `cpp-alerts-lgtm`
suite is now empty and will be auto-generated when building a dist.
This commit has no effect in itself, but these files need to be in place
when the corresponding changes are made in Semmle/code.
As reported in CPP-236, this query has false positives on signed
integers that cannot be negative. It could possibly be improved with a
local range analysis, but the query would most likely still have so many
false positives that we would have to lower its precision.
Under our current policy, this change will make the query hidden by
default on LGTM.
