Cleanup attribute allows users to attach a destructor-like functions
to variable declarations to be called whenever they leave the scope.
The logic of such functions is not supported by the Clang's CFG and
is too hard to be reasoned about. In order to avoid false positives
in this situation, we assume that we didn't see ALL of the executtion
paths of the function and, thus, can warn only about multiple call
violation.
rdar://74441906
Differential Revision: https://reviews.llvm.org/D98694
This patch introduces a very simple inter-procedural analysis
between blocks and enclosing functions.
We always analyze blocks first (analysis is done as part of semantic
analysis that goes side-by-side with the parsing process), and at the
moment of reporting we don't know how that block will be actually
used.
This patch introduces new logic delaying reports of the "never called"
warnings on blocks. If we are not sure that the block will be called
exactly once, we shouldn't warn our users about that. Double calls,
however, don't require such delays. While analyzing the enclosing
function, we can actually decide what we should do with those
warnings.
Additionally, as a side effect, we can be more confident about blocks
in such context and can treat them not as escapes, but as direct
calls.
rdar://74090107
Differential Revision: https://reviews.llvm.org/D98688
This commit makes escapes symmetrical, meaning that having escape
before and after the branching, where parameter is not called on
one of the paths, will have the same effect.
Differential Revision: https://reviews.llvm.org/D98622
It is very common to check callbacks and completion handlers for null.
This patch supports such checks using built-in functions:
* __builtin_expect
* __builtin_expect_with_probablity
* __builtin_unpredictable
rdar://73455388
Differential Revision: https://reviews.llvm.org/D96268
This commit introduces a new attribute `called_once`.
It can be applied to function-like parameters to signify that
this parameter should be called exactly once. This concept
is particularly widespread in asynchronous programs.
Additionally, this commit introduce a new group of dataflow
analysis-based warnings to check this property. It identifies
and reports the following situations:
* parameter is called twice
* parameter is never called
* parameter is not called on one of the paths
Current implementation can also automatically infer `called_once`
attribute for completion handler paramaters that should follow the
same principle by convention. This behavior is OFF by default and
can be turned on by using `-Wcompletion-handler`.
Differential Revision: https://reviews.llvm.org/D92039
rdar://72812043
Valeriy Savchenko