The original bug was discovered in T75057860. Clang front-end emits an AST that looks like this for an co_await expression:
|- ExprWithCleanups
|- -CoawaitExpr
|- -MaterializeTemporaryExpr ... Awaiter
...
|- -CXXMemberCallExpr ... .await_ready
...
|- -CallExpr ... __builtin_coro_resume
...
|- -CXXMemberCallExpr ... .await_resume
...
ExprWithCleanups is responsible for cleaning up (including calling dtors) for the temporaries generated in the wrapping expression).
In the above structure, the __builtin_coro_resume part (which corresponds to the code for the suspend case in the co_await with symmetric transfer), the pseudocode looks like this:
__builtin_coro_resume(
awaiter.await_suspend(
from_address(
__builtin_coro_frame())).address());
One of the temporaries that's generated as part of this code is the coroutine handle returned from awaiter.await_suspend() call. The call returns a handle which is a prvalue (since it's a returned value on the fly). In order to call the address() method on it, it needs to be converted into an xvalue. Hence a materialized temp is created to hold it. This temp will need to be cleaned up eventually. Now, since all cleanups happen at the end of the entire co_await expression, which is after the <coro.suspend> suspension point, the compiler will think that such a temp needs to live across suspensions, and need to be put on the coroutine frame, even though it's only used temporarily just to call address() method.
Such a phenomena not only unnecessarily increases the frame size, but can lead to ASAN failures, if the coroutine was already destroyed as part of the await_suspend() call. This is because if the coroutine was already destroyed, the frame no longer exists, and one can not store anything into it. But if the temporary object is considered to need to live on the frame, it will be stored into the frame after await_suspend() returns.
A fix attempt was done in https://reviews.llvm.org/D87470. Unfortunately it is incorrect. The reason is that cleanups in Clang works more like linearly than nested. There is one current state indicating whether it needs cleanup, and an ExprWithCleanups resets that state. This means that an ExprWithCleanups must be capable of cleaning up all temporaries created in the wrapping expression, otherwise there will be dangling temporaries cleaned up at the wrong place.
I eventually found a walk-around (https://reviews.llvm.org/D89066) that doesn't break any existing tests while fixing the issue. But it targets the final co_await only. If we ever have a co_await that's not on the final awaiter and the frame gets destroyed after suspend, we are in trouble. Hence we need a proper fix.
This patch is the proper fix. It does the folllowing things to fully resolve the issue:
1. The AST has to be generated in the order according to their nesting relationship. We should not generate AST out of order because then the code generator would incorrectly track the state of temporaries and when a cleanup is needed. So the code in buildCoawaitCalls is reorganized so that we will be generating the AST for each coawait member call in order along with their child AST.
2. await_ready() call is wrapped with an ExprWithCleanups so that temporaries in it gets cleaned up as early as possible to avoid living across suspension.
3. await_suspend() call is wrapped with an ExprWithCleanups if it's not a symmetric transfer. In the case of a symmetric transfer, in order to maintain the musttail call contract, the ExprWithCleanups is wraaped before the resume call.
4. In the end, we mark again that it needs a cleanup, so that the entire CoawaitExpr will be wrapped with a ExprWithCleanups which will clean up the Awaiter object associated with the await expression.
Differential Revision: https://reviews.llvm.org/D90990
In https://reviews.llvm.org/D87470 I added the change to tighten the lifetime of the expression awaiter.await_suspend().address.
Howver it was incorrect. ExprWithCleanups will call the dtor and end the lifetime for all the temps created in the current full expr.
When this is called on a normal await call, we don't want to do that.
We only want to do this for the call on the final_awaiter, to avoid writing into the frame after the frame is destroyed.
This change fixes it, by checking IsImplicit.
Differential Revision: https://reviews.llvm.org/D89066
In generating the code for symmetric transfer, a temporary object is created to store the returned handle from await_suspend() call of the awaiter. Previously this temp won't be cleaned up until very later, which ends up causing this temp to be spilled to the heap. However, we know that this temp will no longer be needed after the coro_resume call. We can clean it up right after.
Differential Revision: https://reviews.llvm.org/D87470
User can own a version of coroutine_handle::address() whose return type is not
void* by using template specialization for coroutine_handle<> for some
promise_type.
In this case, the codes may violate the capability with existing async C APIs
that accepted a void* data parameter which was then passed back to the
user-provided callback.
Patch by ChuanqiXu
Differential Revision: https://reviews.llvm.org/D82442
Summary:
Check that the co_await promise.final_suspend() does not potentially throw again after we have resolved dependent types.
This takes care of the cases where promises types are templated.
Added test cases for this scenario and confirmed that the checks happen now.
Also run libcxx tests locally to make sure all tests pass.
Reviewers: Benabik, lewissbaker, junparser, modocache
Reviewed By: modocache
Subscribers: modocache, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D82332
Summary:
In https://reviews.llvm.org/D82029 we added the conformance check that the expression co_await promise.final_suspend() should not potentially throw.
As part of this expression, in cases when the await_suspend() method of the final suspend awaiter returns a handle, __builtin_coro_resume could be called on the handle to immediately resume that coroutine.
__builtin_coro_resume is not declared with noexcept and it shouldn't. We need to special check this case here.
Reviewers: modocache, lewissbaker, junparser
Reviewed By: lewissbaker
Subscribers: modocache, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D82415
Summary:
This patch addresses https://bugs.llvm.org/show_bug.cgi?id=46256
The spec of coroutine requires that the expression co_await promise.final_suspend() shall not be potentially-throwing.
To check this, we recursively look at every call (including Call, MemberCall, OperatorCall and Constructor) in all code
generated by the final suspend, and ensure that the callees are declared with noexcept. We also look at any returned data
type that requires explicit destruction, and check their destructors for noexcept.
This patch does not check declarations with dependent types yet, which will be done in future patches.
Updated all tests to add noexcept to the required functions, and added a dedicated test for this patch.
This patch might start to cause existing codebase fail to compile because most people may not have been strict in tagging
all the related functions noexcept.
Reviewers: lewissbaker, modocache, junparser
Reviewed By: modocache
Subscribers: arphaman, junparser, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D82029
Summary:
In the case of a coroutine that takes no arguments,
`Sema::buildCoroutinePromise` constructs a list-initialization
(`clang::InitializationKind::InitKind::IK_DirectList`) of the
promise variable, using a list of empty arguments. So, if one were to
dump the promise `VarDecl` immediately after `Sema::ActOnCoroutineBodyStart`
calls `checkCoroutineContext`, for a coroutine function that takes no
arguments, they'd see the following:
```
VarDecl 0xb514490 <test.cpp:26:3> col:3 __promise '<dependent type>' callinit
`-ParenListExpr 0xb514510 <col:3> 'NULL TYPE'
```
But after this patch, the `ParenListExpr` is no longer constructed, and
the promise variable uses default initialization
(`clang::InitializationKind::InitKind::IK_Default`):
```
VarDecl 0x63100012dae0 <test.cpp:26:3> col:3 __promise '<dependent type>'
```
As far as I know, there's no case in which list-initialization with no
arguments differs from default initialization, but if I'm wrong please
let me know (and I'll add a test case that demonstrates the change --
but as-is I can't think of a functional test case for this). I think both
comply with the wording of C++20 `[dcl.fct.def.coroutine]p5`:
> _promise-constructor-arguments_ is determined as follows: overload
resolution is performed on a promise constructor call created by
assembling an argument list with lvalues `p1 ... pn`. If a viable
constructor is found (12.4.2), then _promise-constructor-arguments_
is `(p1, ... , pn)`, otherwise _promise-constructor-arguments_ is
empty.
Still, I think this patch is an improvement regardless, because it
reduces the size of the AST.
Reviewers: GorNishanov, rsmith, lewissbaker
Subscribers: EricWF, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D70555
Summary:
The assertion of CoroutineParameterMoves happens when build coroutine function with arguments multiple time while fails to build promise type.
Fix: use return false instead.
Test Plan: check-clang
Reviewers: modocache, GorNishanov, rjmccall
Reviewed By: modocache
Subscribers: rjmccall, EricWF, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D69022
Patch by junparser (JunMa)!
Builtins are rarely if ever accessed via the Preprocessor. They are
typically found on the ASTContext, so there should be no performance
penalty to using a pointer indirection to store the builtin context.
The static analyzer is warning about potential null dereferences, but in these cases we should be able to use castAs<> directly and if not assert will fire for us.
llvm-svn: 373911
Summary:
this revision adds Lexing, Parsing and Basic Semantic for the consteval specifier as specified by http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1073r3.html
with this patch, the consteval specifier is treated as constexpr but can only be applied to function declaration.
Changes:
- add the consteval keyword.
- add parsing of consteval specifier for normal declarations and lambdas expressions.
- add the whether a declaration is constexpr is now represented by and enum everywhere except for variable because they can't be consteval.
- adapt diagnostic about constexpr to print constexpr or consteval depending on the case.
- add tests for basic semantic.
Reviewers: rsmith, martong, shafik
Reviewed By: rsmith
Subscribers: eraman, efriedma, rnkovacs, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D61790
llvm-svn: 363362
Summary:
https://reviews.llvm.org/D59076 added a new coroutine error that
prevented users from using 'co_await' or 'co_yield' within a exception
handler. However, it was reverted in https://reviews.llvm.org/rC356774
because it caused a regression in nested scopes in C++ catch statements,
as documented by https://bugs.llvm.org/show_bug.cgi?id=41171.
The issue was due to an incorrect use of a `clang::ParseScope`. To fix:
1. Add a regression test for catch statement parsing that mimics the bug
report from https://bugs.llvm.org/show_bug.cgi?id=41171.
2. Re-apply the coroutines error patch from
https://reviews.llvm.org/D59076, but this time with the correct
ParseScope behavior.
Reviewers: GorNishanov, tks2103, rsmith, riccibruno, jbulow
Reviewed By: riccibruno
Subscribers: EricWF, jdoerfert, lewissbaker, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D59752
llvm-svn: 356865
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
Summary:
https://reviews.llvm.org/D54862 removed the usages of `ASTContext&` from
within the `CXXMethodDecl::getThisType` method. Remove the parameter
altogether, as well as all usages of it. This does not result in any
functional change because the parameter was unused since
https://reviews.llvm.org/D54862.
Test Plan: check-clang
Reviewers: akyrtzi, mikael
Reviewed By: mikael
Subscribers: mehdi_amini, dexonsmith, cfe-commits
Differential Revision: https://reviews.llvm.org/D56509
llvm-svn: 350914
Rather than sprinkle calls to DiagnoseUnusedExprResult() around in places where we want diagnostics, we now diagnose unused expression statements and full expressions in a more generic way when acting on the final expression statement. This results in more appropriate diagnostics for [[nodiscard]] where we were previously lacking them, such as when the body of a for loop is not a compound statement.
This patch fixes PR39837.
llvm-svn: 350404
Use the newly available space in the bit-fields of Stmt
and store the expressions in a trailing array. This saves
2 pointer per ParenListExpr.
Differential Revision: https://reviews.llvm.org/D54675
Reviewed By: rjmccall
llvm-svn: 347320
Summary:
Addressing https://bugs.llvm.org/show_bug.cgi?id=37265.
Implements [class.copy]/33 of coroutines TS.
When the criteria for elision of a copy/move operation are met, but not
for an exception-declaration, and the object to be copied is designated by an
lvalue, or when the expression in a return or co_return statement is a
(possibly parenthesized) id-expression that names an object with automatic
storage duration declared in the body or parameter-declaration-clause of the
innermost enclosing function or lambda-expression, overload resolution to select
the constructor for the copy or the return_value overload to call is first
performed as if the object were designated by an rvalue.
Patch by Tanoy Sinha!
Reviewers: modocache, GorNishanov
Reviewed By: modocache, GorNishanov
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D51741
llvm-svn: 343949
Summary:
Currently clang looks up the coroutine_traits ClassTemplateDecl
everytime it looks up the promise type. This is unnecessary
as coroutine_traits doesn't change between promise type lookups.
This diff caches the coroutine_traits lookup.
Patch by Tanoy Sinha!
Test Plan:
I added log statements in the new lookupCoroutineTraits function
to ensure that LookupQualifiedName was only called once even
when multiple coroutines existed in the source file.
Reviewers: modocache, GorNishanov
Reviewed By: modocache
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D48981
llvm-svn: 337103
Summary:
Add citations to the Coroutines TS to the `isValidCoroutineContext`
function, as well as a FIXME and test for [expr.await]p2, which states
a co_await expression cannot be used in a default argument.
Test Plan: check-clang
Reviewers: GorNishanov, EricWF
Reviewed By: GorNishanov
Subscribers: rsmith, cfe-commits
Differential Revision: https://reviews.llvm.org/D48519
llvm-svn: 335420
This is similar to the LLVM change https://reviews.llvm.org/D46290.
We've been running doxygen with the autobrief option for a couple of
years now. This makes the \brief markers into our comments
redundant. Since they are a visual distraction and we don't want to
encourage more \brief markers in new code either, this patch removes
them all.
Patch produced by
for i in $(git grep -l '\@brief'); do perl -pi -e 's/\@brief //g' $i & done
for i in $(git grep -l '\\brief'); do perl -pi -e 's/\\brief //g' $i & done
Differential Revision: https://reviews.llvm.org/D46320
llvm-svn: 331834
FunctionProtoType.
We previously re-evaluated the expression each time we wanted to know whether
the type is noexcept or not. We now evaluate the expression exactly once.
This is not quite "no functional change": it fixes a crasher bug during AST
deserialization where we would try to evaluate the noexcept specification in a
situation where we have not deserialized sufficient portions of the AST to
permit such evaluation.
llvm-svn: 331428
Found via codespell -q 3 -I ../clang-whitelist.txt
Where whitelist consists of:
archtype
cas
classs
checkk
compres
definit
frome
iff
inteval
ith
lod
methode
nd
optin
ot
pres
statics
te
thru
Patch by luzpaz! (This is a subset of D44188 that applies cleanly with a few
files that have dubious fixes reverted.)
Differential revision: https://reviews.llvm.org/D44188
llvm-svn: 329399
Summary:
https://reviews.llvm.org/rL325291 implemented Coroutines TS N4723
section [dcl.fct.def.coroutine]/7, but it performed lookup of allocator
functions within both the global and class scope, whereas the specified
behavior is to perform lookup for custom allocators within just the
class scope.
To fix, add parameters to the `Sema::FindAllocationFunctions` function
such that it can be used to lookup allocators in global scope,
class scope, or both (instead of just being able to look up in just global
scope or in both global and class scope). Then, use those parameters
from within the coroutine Sema.
This incorrect behavior had the unfortunate side-effect of causing the
bug https://bugs.llvm.org/show_bug.cgi?id=36578 (or at least the reports
of that bug in C++ programs). That bug would occur for any C++ user with
a coroutine frame that took a single pointer argument, since it would
then find the global placement form `operator new`, described in the
C++ standard 18.6.1.3.1. This patch prevents Clang from generating code
that triggers the LLVM assert described in that bug report.
Test Plan: `check-clang`
Reviewers: GorNishanov, eric_niebler, lewissbaker
Reviewed By: GorNishanov
Subscribers: EricWF, cfe-commits
Differential Revision: https://reviews.llvm.org/D44552
llvm-svn: 328949
When SemaCoroutine looks for await_resume, it means it. No need for helpful: "Did you mean await_ready?" messages.
Fixes PR33477 and a couple of FIXMEs in test/SemaCXX/coroutines.cpp
llvm-svn: 328663
Summary:
Currently an invalid source range is generated for the member call expressions of `co_await`. The end location of the call expression is the `co_await` token loc, while the start is the location of the operand. This causes crashes when the source range is used to produce diagnostics.
This patch fixes the issues by using the expression location instead of the token location when building the member calls.
Reviewers: GorNishanov, rsmith, vsk, aaron.ballman
Reviewed By: vsk
Subscribers: cfe-commits, modocache
Differential Revision: https://reviews.llvm.org/D44915
llvm-svn: 328606
Summary:
This provides no measurable build speedup, but it reinstates an
optimization from r112038 that was lost in r179618. It requires moving
CapturedScopeInfo::Capture out to clang::sema, which might be too
general since we have plenty of other Capture records in BlockDecl and
other AST nodes.
Reviewers: rjmccall
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D44221
llvm-svn: 326957
Summary:
Depends on https://reviews.llvm.org/D42605.
An implementation of the behavior described in `[dcl.fct.def.coroutine]/7`:
when a promise type overloads `operator new` using a "placement new"
that takes the same argument types as the coroutine function, that
overload is used when allocating the coroutine frame.
Simply passing references to the coroutine function parameters directly
to `operator new` results in invariant violations in LLVM's coroutine
splitting pass, so this implementation modifies Clang codegen to
produce allocator-specific alloc/store/loads for each parameter being
forwarded to the allocator.
Test Plan: `check-clang`
Reviewers: rsmith, GorNishanov, eric_niebler
Reviewed By: GorNishanov
Subscribers: lewissbaker, EricWF, cfe-commits
Differential Revision: https://reviews.llvm.org/D42606
llvm-svn: 325291
Summary:
Fix NRVO for Gro variable.
Previously, we only marked the GRO declaration as an NRVO variable
when its QualType and the function return's QualType matched exactly
(using operator==). However, this was incorrect for two reasons:
1. We were marking non-class types, such as ints, as being NRVO variables.
2. We failed to handle cases where the canonical types were the same, but the actual `QualType` objects were different. For example, if one was represented by a typedef. (Example: https://godbolt.org/g/3UFgsL)
This patch fixes these bugs by marking the Gro variable as supporting NRVO only
when `BuildReturnStmt` marks the Gro variable as a coroutine candidate.
Reviewers: rsmith, GorNishanov, nicholas
Reviewed By: GorNishanov
Subscribers: majnemer, cfe-commits
Differential Revision: https://reviews.llvm.org/D42343
llvm-svn: 324037
Summary:
Fix NRVO for Gro variable.
Previously, we only marked the GRO declaration as an NRVO variable
when its QualType and the function return's QualType matched exactly
(using operator==). However, this was incorrect for two reasons:
1. We were marking non-class types, such as ints, as being NRVO variables.
2. We failed to handle cases where the canonical types were the same, but the actual `QualType` objects were different. For example, if one was represented by a typedef. (Example: https://godbolt.org/g/3UFgsL)
This patch fixes these bugs by marking the Gro variable as supporting NRVO only
when `BuildReturnStmt` marks the Gro variable as a coroutine candidate.
Reviewers: rsmith, GorNishanov, nicholas
Reviewed By: GorNishanov
Subscribers: majnemer, cfe-commits
Differential Revision: https://reviews.llvm.org/D42343
llvm-svn: 323712
Summary:
Use corutine function arguments to initialize a promise type, but only
if the promise type defines a constructor that takes those arguments.
Otherwise, fall back to the default constructor.
Test Plan: check-clang
Reviewers: rsmith, GorNishanov, eric_niebler
Reviewed By: GorNishanov
Subscribers: toby-allsopp, lewissbaker, EricWF, cfe-commits
Differential Revision: https://reviews.llvm.org/D41820
llvm-svn: 323381
Summary:
If await_suspend returns a coroutine_handle, as in the example below:
```
coroutine_handle<> await_suspend(coroutine_handle<> h) {
coro.promise().waiter = h;
return coro;
}
```
suspensionExpression processing will resume the coroutine pointed at by that handle.
Related LLVM change rL311751 makes resume calls of this kind `musttail` at any optimization level.
This enables unlimited symmetric control transfer from coroutine to coroutine without blowing up the stack.
Reviewers: GorNishanov
Reviewed By: GorNishanov
Subscribers: rsmith, EricWF, cfe-commits
Differential Revision: https://reviews.llvm.org/D37131
llvm-svn: 311762
Summary:
Currently we build the co_await expressions on the wrong implicit statements of the implicit ranged for; Specifically we build the co_await expression wrapping the range declaration, but it should wrap the begin expression.
This patch fixes co_await on range for.
Reviewers: rsmith, GorNishanov
Reviewed By: GorNishanov
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D34021
llvm-svn: 305363
Summary:
We were not handling correctly rebuilding of parameter and were not creating copies for them.
Now we will always rebuild parameter moves in TreeTransform's TransformCoroutineBodyStmt.
Reviewers: rsmith, GorNishanov
Reviewed By: rsmith
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D33797
llvm-svn: 304620
Chuanqi Xu