Previous changes like D101202 and D104261 have eliminated the special
status that break and continue once had, since now we're making
decisions purely based on the structure of the CFG without regard for
the underlying source code constructs.
This means we don't gain anything from defering handling for these
blocks. Dropping it moves some diagnostics, though arguably into a
better place. We're working around a "quirk" in the CFG that perhaps
wasn't visible before: while loops have an empty "transition block"
where continue statements and the regular loop exit meet, before
continuing to the loop entry. To get a source location for that, we
slightly extend our handling for empty blocks. The source location for
the transition ends up to be the loop entry then, but formally this
isn't a back edge. We pretend it is anyway. (This is safe: we can always
treat edges as back edges, it just means we allow less and don't modify
the lock set. The other way around it wouldn't be safe.)
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D106715
Previously in D104261 we warned about dropping locks from back edges,
this is the corresponding change for exclusive/shared joins. If we're
entering the loop with an exclusive change, which is then relaxed to a
shared lock before we loop back, we have already analyzed the loop body
with the stronger exclusive lock and thus might have false positives.
There is a minor non-observable change: we modify the exit lock set of a
function, but since that isn't used further it doesn't change anything.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D106713
In D104261 we made the parameters' meaning slightly more specific, this
changes their names accordingly. In all uses we're building a new lock
set by intersecting existing locksets. The first (modifiable) argument
is the new lock set being built, the second (non-modifiable) argument is
the exit set of a preceding block.
Reviewed By: aaron.ballman, delesley
Differential Revision: https://reviews.llvm.org/D104649
We allow branches to join where one holds a managed lock but the other
doesn't, but we can't do so for back edges: because there we can't drop
them from the lockset, as we have already analyzed the loop with the
larger lockset. So we can't allow dropping managed locks on back edges.
We move the managed() check from handleRemovalFromIntersection up to
intersectAndWarn, where we additionally check if we're on a back edge if
we're removing from the first lock set (the entry set of the next block)
but not if we're removing from the second lock set (the exit set of the
previous block). Now that the order of arguments matters, I had to swap
them in one invocation, which also causes some minor differences in the
tests.
Reviewed By: delesley
Differential Revision: https://reviews.llvm.org/D104261
This renames the expression value categories from rvalue to prvalue,
keeping nomenclature consistent with C++11 onwards.
C++ has the most complicated taxonomy here, and every other language
only uses a subset of it, so it's less confusing to use the C++ names
consistently, and mentally remap to the C names when working on that
context (prvalue -> rvalue, no xvalues, etc).
Renames:
* VK_RValue -> VK_PRValue
* Expr::isRValue -> Expr::isPRValue
* SK_QualificationConversionRValue -> SK_QualificationConversionPRValue
* JSON AST Dumper Expression nodes value category: "rvalue" -> "prvalue"
Signed-off-by: Matheus Izvekov <mizvekov@gmail.com>
Reviewed By: rsmith
Differential Revision: https://reviews.llvm.org/D103720
Similar to how we allow managed and asserted locks to be held and not
held in joining branches, we also allow them to be held shared and
exclusive. The scoped lock should restore the original state at the end
of the scope in any event, and asserted locks need not be released.
We should probably only allow asserted locks to be subsumed by managed,
not by (directly) acquired locks, but that's for another change.
Reviewed By: delesley
Differential Revision: https://reviews.llvm.org/D102026
It's going to become a bit more complicated, so let's have it separate.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D102025
We were modifying precisely when intersecting the lock sets of multiple
predecessors without back edge. That's no coincidence: we can't modify
on back edges, it doesn't make sense to modify at the end of a function,
and otherwise we always want to intersect on forward edges, because we
can build a new lock set for those.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D101755
We weren't modifying the lock set when intersecting with one coming
from a break-terminated block. This is inconsistent, since break isn't a
back edge, and it leads to false negatives with scoped locks. We usually
don't warn for those when joining locksets aren't the same, we just
silently remove locks that are not in the intersection. But not warning
and not removing them isn't right.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D101202
The motivation here is to make it available in the base class whether a
fact is managed or not. That would have meant three flags on the base
class, so I had a look whether we really have 8 possible combinations.
It turns out we don't: asserted and declared are obviously mutually
exclusive. Managed facts are only created when we acquire a capability
through a scoped capability. Adopting an asserted or declared lock will
not (in fact can not, because Facts are immutable) make them managed.
We probably don't want to allow adopting an asserted lock (because then
the function should probably have a release attribute, and then the
assertion is pointless), but we might at some point decide to replace a
declared fact on adoption.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D100801
Instead of conditionally overwriting a nullptr and then branching on its
nullness, just branch directly on the original condition. Then we can
make both pointers (non-null) references instead.
We already did so for scoped locks acquired in the constructor, this
change extends the treatment to deferred locks and scoped unlocking, so
locks acquired outside of the constructor. Obviously this makes things
more consistent.
Originally I thought this was a bad idea, because obviously it
introduces false negatives when it comes to double locking, but these
are typically easily found in tests, and the primary goal of the Thread
safety analysis is not to find double locks but race conditions.
Since the scoped lock will release the mutex anyway when the scope ends,
the inconsistent state is just temporary and probably fine.
Reviewed By: delesley
Differential Revision: https://reviews.llvm.org/D98747
Currently we want to allow calling non-const methods even when only a
shared lock is held, because -Wthread-safety-reference is already quite
sensitive and not all code is const-correct. Even if it is, this might
require users to add std::as_const around the implicit object argument.
See D52395 for a discussion.
Fixes PR46963.
The constructor of Project asserts that the contained ValueDecl is not
null, use that in the ThreadSafetyAnalyzer. In the case of LiteralPtr
it's the other way around.
Also dyn_cast<> is sufficient if we know something isn't null.
Instead of just mutex members we also consider mutex globals.
Unsurprisingly they are always in scope. Now the paper [1] says that
> The scope of a class member is assumed to be its enclosing class,
> while the scope of a global variable is the translation unit in
> which it is defined.
But I don't think we should limit this to TUs where a definition is
available - a declaration is enough to acquire the mutex, and if a mutex
is really limited in scope to a translation unit, it should probably be
only declared there.
The previous attempt in 9dcc82f34e was causing false positives because
I wrongly assumed that LiteralPtrs were always globals, which they are
not. This should be fixed now.
[1] https://static.googleusercontent.com/media/research.google.com/en/us/pubs/archive/42958.pdf
Fixes PR46354.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D84604
Instead of just mutex members we also consider mutex globals.
Unsurprisingly they are always in scope. Now the paper [1] says that
> The scope of a class member is assumed to be its enclosing class,
> while the scope of a global variable is the translation unit in
> which it is defined.
But I don't think we should limit this to TUs where a definition is
available - a declaration is enough to acquire the mutex, and if a mutex
is really limited in scope to a translation unit, it should probably be
only declared there.
[1] https://static.googleusercontent.com/media/research.google.com/en/us/pubs/archive/42958.pdf
Fixes PR46354.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D84604
Other warning messages for negative capabilities also mention their
kind, and the double space was ugly.
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D84603
Summary:
When getting a warning that we release a capability that isn't held it's
sometimes not clear why. So just like we do for double locking, we add a
note on the previous release operation, which marks the point since when
the capability isn't held any longer.
We can find this previous release operation by looking up the
corresponding negative capability.
Reviewers: aaron.ballman, delesley
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D81352
Summary:
The standard std::unique_lock can be constructed to manage a lock without
initially acquiring it by passing std::defer_lock as second parameter.
It can be acquired later by calling lock().
To support this, we use the locks_excluded attribute. This might seem
like an odd choice at first, but its consistent with the other
annotations we support on scoped capability constructors. By excluding
the lock we state that it is currently not in use and the function
doesn't change that, which is exactly what the constructor does.
Along the way we slightly simplify handling of scoped capabilities.
Reviewers: aaron.ballman, delesley
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D81332
-Wthread-safety was failing to detect certain AST patterns it should
detect. Make the pattern detection a bit more comprehensive.
Due to an unrelated bug involving template instantiation, this showed up
as a regression in 10.0 vs. 9.0 in the original bug report. The included
testcase fails on older versions of clang, though.
Fixes https://bugs.llvm.org/show_bug.cgi?id=45323 .
Differential Revision: https://reviews.llvm.org/D76943
Summary:
This happens when someone initializes a variable with guaranteed copy
elision and an added const qualifier. Fixes PR43826.
Reviewers: aaron.ballman, rsmith
Reviewed By: aaron.ballman
Differential Revision: https://reviews.llvm.org/D69533
Now that we've moved to C++14, we no longer need the llvm::make_unique
implementation from STLExtras.h. This patch is a mechanical replacement
of (hopefully) all the llvm::make_unique instances across the monorepo.
Differential revision: https://reviews.llvm.org/D66259
llvm-svn: 368942
Turn it into a variant class instead. This conversion does indeed save some code
but there's a plan to add support for more kinds of terminators that aren't
necessarily based on statements, and with those in mind it becomes more and more
confusing to have CFGTerminators implicitly convertible to a Stmt *.
Differential Revision: https://reviews.llvm.org/D61814
llvm-svn: 361586
Summary:
Similar to D56967, we add the existing diag::note_locked_here to tell
the user where we saw the locking that isn't matched correctly.
Reviewers: aaron.ballman, delesley
Reviewed By: aaron.ballman
Subscribers: cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D59455
llvm-svn: 356427
Summary:
We use the existing diag::note_locked_here to tell the user where we saw
the first locking.
Reviewers: aaron.ballman, delesley
Reviewed By: aaron.ballman
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D56967
llvm-svn: 352549
to reflect the new license.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351636
All of the other constructors already take a reference to the AST context.
This avoids calling Decl::getASTContext in most cases. Additionally move
the definition of the constructor from Expr.h to Expr.cpp since it is calling
DeclRefExpr::computeDependence. NFC.
llvm-svn: 349901
Summary:
The pattern is problematic with C++ exceptions, and not as widespread as
scoped locks, but it's still used by some, for example Chromium.
We are a bit stricter here at join points, patterns that are allowed for
scoped locks aren't allowed here. That could still be changed in the
future, but I'd argue we should only relax this if people ask for it.
Fixes PR36162.
Reviewers: aaron.ballman, delesley, pwnall
Reviewed By: delesley, pwnall
Subscribers: pwnall, cfe-commits
Differential Revision: https://reviews.llvm.org/D52578
llvm-svn: 349300
A ConstantExpr class represents a full expression that's in a context where a
constant expression is required. This class reflects the path the evaluator
took to reach the expression rather than the syntactic context in which the
expression occurs.
In the future, the class will be expanded to cache the result of the evaluated
expression so that it's not needlessly re-evaluated
Reviewed By: rsmith
Differential Revision: https://reviews.llvm.org/D53475
llvm-svn: 345692
Summary:
We unwrap conditional expressions containing try-lock functions.
Additionally we don't acquire on conditional expression branches, since
that is usually not helpful. When joining the branches we would almost
certainly get a warning then.
Hopefully fixes an issue that was raised in D52398.
Reviewers: aaron.ballman, delesley, hokein
Reviewed By: aaron.ballman
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D52888
llvm-svn: 343902
Summary:
Instead of only examining call arguments, we also examine constructor
arguments applying the same rules.
That was an opportunity for refactoring the examination procedure to
work with iterators instead of integer indices. For the case of
CallExprs no functional change is intended.
Reviewers: aaron.ballman, delesley
Reviewed By: delesley
Subscribers: JonasToth, cfe-commits
Differential Revision: https://reviews.llvm.org/D52443
llvm-svn: 343831
Summary:
When people are really sure they'll get the lock they sometimes use
__builtin_expect. It's also used by some assertion implementations.
Asserting that try-lock succeeded is basically the same as asserting
that the lock is not held by anyone else (and acquiring it).
Reviewers: aaron.ballman, delesley
Reviewed By: aaron.ballman
Subscribers: kristina, cfe-commits
Differential Revision: https://reviews.llvm.org/D52398
llvm-svn: 343681
Not used productively, so no observable functional change.
Note that printSCFG doesn't yet work reliably, it seems to crash
sometimes.
llvm-svn: 342790
Summary:
It's already allowed to prematurely release a scoped lock, now we also
allow relocking it again, possibly even in another mode.
This is the second attempt, the first had been merged as r339456 and
reverted in r339558 because it caused a crash.
Reviewers: delesley, aaron.ballman
Reviewed By: delesley, aaron.ballman
Subscribers: hokein, cfe-commits
Differential Revision: https://reviews.llvm.org/D49885
llvm-svn: 340459
Benjamin Kramer