Remove constraint that an initializing expression of struct type must have an
associated `Value`. This invariant is not and will not be guaranteed by the
framework, because of potentially uninitialized fields.
Differential Revision: https://reviews.llvm.org/D123961
Currently, when the framework is used with an analysis that does not override
`compareEquivalent`, it does not terminate for most loops. The root cause is the
interaction of (the default implementation of) environment comparison
(`compareEquivalent`) and the means by which locations and values are
allocated. Specifically, the creation of certain values (including: reference
and pointer values; merged values) results in allocations of fresh locations in
the environment. As a result, analysis of even trivial loop bodies produces
different (if isomorphic) environments, on identical inputs. At the same time,
the default analysis relies on strict equality (versus some relaxed notion of
equivalence). Together, when the analysis compares these isomorphic, yet
unequal, environments, to determine whether the successors of the given block
need to be (re)processed, the result is invariably "yes", thus preventing loop
analysis from reaching a fixed point.
There are many possible solutions to this problem, including equivalence that is
less than strict pointer equality (like structural equivalence) and/or the
introduction of an explicit widening operation. However, these solutions will
require care to be implemented correctly. While a high priority, it seems more
urgent that we fix the current default implentation to allow
termination. Therefore, this patch proposes, essentially, to change the default
comparison to trivally equate any two values. As a result, we can say precisely
that the analysis will process the loop exactly twice -- once to establish an
initial result state and the second to produce an updated result which will
(always) compare equal to the previous. While clearly unsound -- we are not
reaching a fix point of the transfer function, in practice, this level of
analysis will find many practical issues where a single iteration of the loop
impacts abstract program state.
Note, however, that the change to the default `merge` operation does not affect
soundness, because the framework already produces a fresh (sound) abstraction of
the value when the two values are distinct. The previous setting was overly
conservative.
Differential Revision: https://reviews.llvm.org/D123586
This patch adds basic modeling of `__builtin_expect`, just to propagate the
(first) argument, making the call transparent.
Driveby: adds tests for proper handling of other builtins.
Differential Revision: https://reviews.llvm.org/D122908
This patch extends the join logic for environments to explicitly handle
boolean values. It creates the disjunction of both source values, guarded by the
respective flow conditions from each input environment. This change allows the
framework to reason about boolean correlations across multiple branches (and
subsequent joins).
Differential Revision: https://reviews.llvm.org/D122838
Currently, the framework does not track derived class access to base
fields. This patch adds that support and a corresponding test.
Differential Revision: https://reviews.llvm.org/D122273
This patch adds limited modeling of the `value_or` method. Specifically, when
used in a particular idiom in a comparison to implicitly check whether the
optional holds a value.
Differential Revision: https://reviews.llvm.org/D122231
This patch provides the user with the ability to disable all checked of accesses
to optionals that are the pointees of smart pointers. Since smart pointers are
not modeled (yet), the system cannot distinguish safe from unsafe accesses to
optionals through smart pointers. This results in false positives whenever
optionals are used through smart pointers. The patch gives the user the choice
of ignoring all positivess in these cases.
Differential Revision: https://reviews.llvm.org/D122143
Chromium's implementation of assertions (`CHECK`, `DCHECK`, etc.) are not
annotated with "noreturn", by default. This patch adds a model of the logical
implications of successfully executing one of these assertions.
Differential Revision: https://reviews.llvm.org/D121797
Terminators are handled specially in the transfer functions so we need an
additional check on whether the analysis has disabled built-in transfer
functions.
Differential Revision: https://reviews.llvm.org/D121694
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Differential Revision: https://reviews.llvm.org/D121455
This commit reverts e0cc28dfdc and moves
UncheckedOptionalAccessModelTest.cpp into clang/unittests/Analysis/FlowSensitive,
to avoid build failures. The test will be moved back into a Models subdir
in a follow up patch that will address the build configuration issues.
Original description:
Adds a dataflow analysis that detects unsafe accesses to values of type
`std::optional`, `absl::optional`, or `base::Optional`.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D121197
This enables tests out of clang/unittests/Analysis/FlowSensitive to
use the testing support utilities.
Reviewed-by: ymandel, gribozavr2
Differential Revision: https://reviews.llvm.org/D121285
Adds a dataflow analysis that detects unsafe accesses to values of type
`std::optional`, `absl::optional`, or `base::Optional`.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D121197
When pre-initializing fields in the environment, the code assumed that all
fields of a struct would be initialized. However, given limits on value
construction, that assumption is incorrect. This patch changes the code to drop
that assumption and thereby avoid dereferencing a nullptr.
Differential Revision: https://reviews.llvm.org/D121158
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D120984
This patch adds a simpe lattice used to collect source loctions. An intended application is to track errors found in code during an analysis.
Differential Revision: https://reviews.llvm.org/D120890
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D120711
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D120289
Adds two new parameters to control the size of data structures modeled in the environment: # of values and depth of data structure. The environment already prevents creation of recursive data structures, but that was insufficient in practice. Very large structs still ground the analysis to a halt. These new parameters allow tuning the size more effectively.
In this patch, the parameters are set as internal constants. We leave to a future patch to make these proper model parameters.
Differential Revision: https://reviews.llvm.org/D120510
When assigning a value to a storage location of a struct member we
need to also update the value in the corresponding `StructValue`.
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D120414
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D120149
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D119953
This will be necessary later when we add support for evaluating logic
expressions such as && and ||.
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D119447
Make specializations of `DataflowAnalysis` extendable with domain-specific
logic for comparing distinct values when comparing environments.
This includes a breaking change to the `runDataflowAnalysis` interface
as the return type is now `llvm::Expected<...>`.
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D118596
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D118480
These built-in functions build the (sophisticated) model of the code's
memory. This model isn't used by all analyses, so we provide for disabling it to
avoid incurring the costs associated with its construction.
Differential Revision: https://reviews.llvm.org/D118178
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D118236
Make specializations of `DataflowAnalysis` extendable with domain-specific
logic for merging distinct values when joining environments. This could be
a strict lattice join or a more general widening operation.
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D118038
This patch ensures that the dataflow analysis framework does not crash
when it encounters access to members of union types.
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D118226
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D118119
unsigned is technically guaranteed to be only 16 bits in which case 1 << 16 would wrap around to zero.
Differential Revision: https://reviews.llvm.org/D117938
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D117754
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D117667
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D117567
The FIXME is no longer relevant as ControlFlowContext centralizes the
construction of the CFG.
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D117563
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D117496
Since Environment's setValue method already does part of the work that
initValueInStorageLocation does, we can factor out a new createValue
method to reduce the duplication.
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D117493
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Differential Revision: https://reviews.llvm.org/D117339
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D117218
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D117123
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: ymandel, xazax.hun
Differential Revision: https://reviews.llvm.org/D117012
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Differential Revision: https://reviews.llvm.org/D116596
Currently, the transfer function returns a new lattice element, which forces an
unnecessary copy on processing each CFG statement.
Differential Revision: https://reviews.llvm.org/D116834
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed-by: xazax.hun
Differential Revision: https://reviews.llvm.org/D116368
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed By: xazax.hun, gribozavr2
Differential Revision: https://reviews.llvm.org/D116022
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed By: xazax.hun, gribozavr2
Differential Revision: https://reviews.llvm.org/D115235
This is part of the implementation of the dataflow analysis framework.
See "[RFC] A dataflow analysis framework for Clang AST" on cfe-dev.
Reviewed By: ymandel, xazax.hun, gribozavr2
Differential Revision: https://reviews.llvm.org/D114234
Yitzhak Mandelbaum