NoQ added a comment.
Thanks for adding me!
Hmm, i think a matcher-based solution would be pretty limited. This is
definitely your typical all-path data-flow problem because you want to make
sure that you're looking at the //last// assignment to the variable.
For example:
int *m = new int;
m = nullptr;
if (m == nullptr) { ... } // no-warning
but
int *m = nullptr;
m = new int;
if (m == nullptr) { ... } // expected-warning{{}}
You might be able to fix false positives by adding a condition that the
variable is not re-assigned within the function (with the help of assignment
operator or due to taking a non-constant reference to it, etc). But you'll end
up with a checker that finds a lot less bugs than a full-featured data flow
analysis could have found. There's a canonical implementation of "the variable
is not modified" check via ASTMatchers in `LoopUnrolling.cpp`.
If you'll ever want to find a full-featured data flow check, i'm not sure but
you might be able to re-use `LiveVariables` analysis (the non-`Relaxed` one) to
find the last assignment, and in this case you won't have to write data flow
analysis yourself. `DeadStores` checker has an example of that.
Repository:
rC Clang
https://reviews.llvm.org/D47554
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