This patch, by hamzasood, implements P0409R2, and allows [=, this] pre-C++2a as an extension (with appropriate warnings) for consistency.
https://reviews.llvm.org/D36572
Thanks Hamza!
llvm-svn: 311224
Summary:
Warn when a lambda explicitly captures something that is not used in its body.
The warning is part of -Wunused and can be enabled with -Wunused-lambda-capture.
Reviewers: rsmith, arphaman, jbcoe, aaron.ballman
Subscribers: Quuxplusone, arphaman, cfe-commits
Differential Revision: https://reviews.llvm.org/D28467
llvm-svn: 291905
This implements something like the current direction of DR1581: we use a narrow
syntactic check to determine the set of places where a constant expression
could be evaluated, and only instantiate a constexpr function or variable if
it's referenced in one of those contexts, or is odr-used.
It's not yet clear whether this is the right set of syntactic locations; we
currently consider all contexts within templates that would result in odr-uses
after instantiation, and contexts within list-initialization (narrowing
conversions take another victim...), as requiring instantiation. We could in
principle restrict the former cases more (only const integral / reference
variable initializers, and contexts in which a constant expression is required,
perhaps). However, this is sufficient to allow us to accept libstdc++ code,
which relies on GCC's behavior (which appears to be somewhat similar to this
approach).
llvm-svn: 291318
Implement lambda capture of *this by copy.
For e.g.:
struct A {
int d = 10;
auto foo() { return [*this] (auto a) mutable { d+=a; return d; }; }
};
auto L = A{}.foo(); // A{}'s lifetime is gone.
// Below is still ok, because *this was captured by value.
assert(L(10) == 20);
assert(L(100) == 120);
If the capture was implicit, or [this] (i.e. *this was captured by reference), this code would be otherwise undefined.
Implementation Strategy:
- amend the parser to accept *this in the lambda introducer
- add a new king of capture LCK_StarThis
- teach Sema::CheckCXXThisCapture to handle by copy captures of the
enclosing object (i.e. *this)
- when CheckCXXThisCapture does capture by copy, the corresponding
initializer expression for the closure's data member
direct-initializes it thus making a copy of '*this'.
- in codegen, when assigning to CXXThisValue, if *this was captured by
copy, make sure it points to the corresponding field member, and
not, unlike when captured by reference, what the field member points
to.
- mark feature as implemented in svn
Much gratitude to Richard Smith for his carefully illuminating reviews!
llvm-svn: 263921
std::initializer_list<T> type. Instead, the list must contain a single element
and the type is deduced from that.
In Clang 3.7, we warned by default on all the cases that would change meaning
due to this change. In Clang 3.8, we will support only the new rules -- per
the request in N3922, this change is applied as a Defect Report against earlier
versions of the C++ standard.
This change is not entirely trivial, because for lambda init-captures we
previously did not track the difference between direct-list-initialization and
copy-list-initialization. The difference was not previously observable, because
the two forms of initialization always did the same thing (the elements of the
initializer list were always copy-initialized regardless of the initialization
style used for the init-capture).
llvm-svn: 252688
If a function declaration is found inside a template function as in:
template<class T> void f() {
void g(int x = T::v) except(T::w);
}
it must be instantiated along with the enclosing template function,
including default arguments and exception specification.
Together with the patch committed in r240974 this implements DR1484.
Differential Revision: http://reviews.llvm.org/D11194
llvm-svn: 245810
The error has the form ... 'int' ... 'const int' ... dropped qualifiers. At
first glance, it appears that the const qualifier is added. Reverse the types
so that the second type is less qualified than the first.
llvm-svn: 237482
Previously we'd try to perform checks on the captures from the middle of
parsing the lambda's body, at the point where we detected that a variable
needed to be captured. This was wrong in a number of subtle ways. In
PR23334, we couldn't correctly handle the list of potential odr-uses
resulting from the capture, and our attempt to recover from that resulted
in a use-after-free.
We now defer building the initialization expression until we leave the lambda
body and return to the enclosing context, where the initialization does the
right thing. This patch only covers lambda-expressions, but we should apply
the same change to blocks and captured statements too.
llvm-svn: 235921
(or of a lambda init-capture, which is sort-of such a variable). The semantics
of such constructs will change when we implement N3922, so we intend to warn on
this in Clang 3.6 then change the semantics in Clang 3.7.
llvm-svn: 228792
Previously if an enumeration was used in a nested name specifier in pre-C++11
language dialect, error message was 'XXX is not a class, namespace, or scoped
enumeration'. This patch removes the word 'scoped' as in C++11 any enumeration
may be used in this context.
llvm-svn: 226410
Specifically, when we have this situation:
struct A {
template <typename T> struct B {
int m1 = sizeof(A);
};
B<int> m2;
};
We can't parse m1's initializer eagerly because we need A to be
complete. Therefore we wait until the end of A's class scope to parse
it. However, we can trigger instantiation of B before the end of A,
which will attempt to instantiate the field decls eagerly, and it would
build a bad field decl instantiation that said it had an initializer but
actually lacked one.
Fixed by deferring instantiation of default member initializers until
they are needed during constructor analysis. This addresses a long
standing FIXME in the code.
Fixes PR19195.
Reviewed By: rsmith
Differential Revision: http://reviews.llvm.org/D5690
llvm-svn: 222192
For namespaces, this is consistent with mangling and GCC's debug info
behavior. For structs, GCC uses <anonymous struct> but we prefer
consistency between all anonymous entities but don't want to confuse
them with template arguments, etc, so we'll just go with parens in all
cases.
llvm-svn: 205398
The problem here is more serious than the fix implies. Adding a field
to a class updates the triviality bits for the class (among other
things). Failing to require a complete type before adding the field
meant that these updates don't happen in the well-formed case where
the capture is an uninstantiated class template specialization,
leading the lambda itself to be treated as having a trivial copy
constructor when it shouldn't. Fixes <rdar://problem/15560464>.
llvm-svn: 197623
Both Richard and I felt that the current wording in the working paper needed some tweaking - Please see http://llvm-reviews.chandlerc.com/D2035 for additional context and references to core-reflector messages that discuss wording tweaks.
What is implemented is what we had intended to specify in Bristol; but, recently felt that the specification might benefit from some tweaking and fleshing.
As a rough attempt to explain the semantics: If a nested lambda with a default-capture names a variable within its body, and if the enclosing full expression that contains the name of that variable is instantiation-dependent - then an enclosing lambda that is capture-ready (i.e. within a non-dependent context) must capture that variable, if all intervening nested lambdas can potentially capture that variable if they need to, and all intervening parent lambdas of the capture-ready lambda can and do capture the variable.
Of note, 'this' capturing is also currently underspecified in the working paper for generic lambdas. What is implemented here is if the set of candidate functions in a nested generic lambda includes both static and non-static member functions (regardless of viability checking - i.e. num and type of parameters/arguments) - and if all intervening nested-inner lambdas between the capture-ready lambda and the function-call containing nested lambda can capture 'this' and if all enclosing lambdas of the capture-ready lambda can capture 'this', then 'this' is speculatively captured by that capture-ready lambda.
Hopefully a paper for the C++ committee (that Richard and I had started some preliminary work on) is forthcoming.
This essentially makes generic lambdas feature complete, except for known bugs. The more prominent ones (and the ones I am currently aware of) being:
- generic lambdas and init-captures are broken - but a patch that fixes this is already in the works ...
- nested variadic expansions such as:
auto K = [](auto ... OuterArgs) {
vp([=](auto ... Is) {
decltype(OuterArgs) OA = OuterArgs;
return 0;
}(5)...);
return 0;
};
auto M = K('a', ' ', 1, " -- ", 3.14);
currently cause crashes. I think I know how to fix this (since I had done so in my initial implementation) - but it will probably take some work and back & forth with Doug and Richard.
A warm thanks to all who provided feedback - and especially to Doug Gregor and Richard Smith for their pivotal guidance: their insight and prestidigitation in such matters is boundless!
Now let's hope this commit doesn't upset the buildbot gods ;)
Thanks!
llvm-svn: 194188
A previous attempt http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20130930/090049.html resulted in PR 17476, and was reverted,
The original TransformLambdaExpr (pre generic-lambdas) transformed the TypeSourceInfo of the Call operator in its own instantiation scope via TransformType. This resulted in the parameters of the call operator being mapped to their transformed counterparts in an instantiation scope that would get popped off.
Then a call to TransformFunctionParameters would add the parameters and their transformed mappings (but newly created ones!) to the current instantiation scope. This would result in a disconnect between the new call operator's TSI parameters and those used to construct the call operator declaration. This was ok in the non-generic lambda world - but would cause issues with nested transformations (when non-generic and generics were interleaved) in the generic lambda world - that I somewhat kludged around initially - but this resulted in PR17476.
The new approach seems cleaner. We only do the transformation of the TypeSourceInfo - but we make sure to do it in the current instantiation scope so we don't lose the untransformed to transformed mappings of the ParmVarDecls when they get created.
Another attempt caused a test to fail (http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20131021/091533.html) and also had to be reverted - my apologies - in my haste, i did not run all the tests - argh!
Now all the tests seem to pass - but a Fixme has been added - since I suspect Richard will find the fix a little inelegant ;) I shall try and work on a more elegant fix once I have had a chance to discuss with Richard or Doug at a later date.
Hopefully the third time;s a charm *fingers crossed*
This does not yet include capturing.
Please see test file for examples.
This patch was LGTM'd by Doug:
http://llvm-reviews.chandlerc.com/D1784
llvm-svn: 193230
They were causing CodeGenCXX/mangle-exprs.cpp to fail.
Revert "Remove the circular reference to LambdaExpr in CXXRecordDecl."
Revert "Again: Teach TreeTransform and family how to transform generic lambdas nested within templates and themselves."
llvm-svn: 193226
lambdas nested within templates and themselves.
A previous attempt http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20130930/090049.html resulted in PR 17476, and was reverted,
The original TransformLambdaExpr (pre generic-lambdas) transformed the TypeSourceInfo of the Call operator in its own instantiation scope via TransformType. This resulted in the parameters of the call operator being mapped to their transformed counterparts in an instantiation scope that would get popped off.
Then a call to TransformFunctionParameters would add the parameters and their transformed mappings (but newly created ones!) to the current instantiation scope. This would result in a disconnect between the new call operator's TSI parameters and those used to construct the call operator declaration. This was ok in the non-generic lambda world - but would cause issues with nested transformations (when non-generic and generics were interleaved) in the generic lambda world - that I somewhat kludged around initially - but this resulted in PR17476.
The new approach seems cleaner. We only do the transformation of the TypeSourceInfo - but we make sure to do it in the current instantiation scope so we don't lose the untransformed to transformed mappings of the ParmVarDecls when they get created.
This does not yet include capturing.
Please see test file for examples.
This patch was LGTM'd by Doug:
http://llvm-reviews.chandlerc.com/D1784
llvm-svn: 193216
This does not yet include capturing (that is next).
Please see test file for examples.
This patch was LGTM'd by Doug:
http://llvm-reviews.chandlerc.com/D1784http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20130930/090048.html
When I first committed this patch - a bunch of buildbots were unable to compile the code that VS2010 seemed to compile. Seems like there was a dependency on Sema/Template.h which VS did not seem to need, but I have now added for the other compilers. It still compiles on Visual Studio 2010 - lets hope the buildbots remain quiet (please!)
llvm-svn: 191879
This does not yet include capturing (that is next).
Please see test file for examples.
This patch was LGTM'd by Doug:
http://llvm-reviews.chandlerc.com/D1784
llvm-svn: 191875
The general strategy is to create template versions of the conversion function and static invoker and then during template argument deduction of the conversion function, create the corresponding call-operator and static invoker specializations, and when the conversion function is marked referenced generate the body of the conversion function using the corresponding static-invoker specialization. Similarly, Codegen does something similar - when asked to emit the IR for a specialized static invoker of a generic lambda, it forwards emission to the corresponding call operator.
This patch has been reviewed in person both by Doug and Richard. Richard gave me the LGTM.
A few minor changes:
- per Richard's request i added a simple check to gracefully inform that captures (init, explicit or default) have not been added to generic lambdas just yet (instead of the assertion violation).
- I removed a few lines of code that added the call operators instantiated parameters to the currentinstantiationscope. Not only did it not handle parameter packs, but it is more relevant in the patch for nested lambdas which will follow this one, and fix that problem more comprehensively.
- Doug had commented that the original implementation strategy of using the TypeSourceInfo of the call operator to create the static-invoker was flawed and allowed const as a member qualifier to creep into the type of the static-invoker. I currently kludge around it - but after my initial discussion with Doug, with a follow up session with Richard, I have added a FIXME so that a more elegant solution that involves the use of TrivialTypeSourceInfo call followed by the correct wiring of the template parameters to the functionprototypeloc is forthcoming.
Thanks!
llvm-svn: 191634
Specifically, the following features are not included in this commit:
- any sort of capturing within generic lambdas
- generic lambdas within template functions and nested
within other generic lambdas
- conversion operator for captureless lambdas
- ensuring all visitors are generic lambda aware
(Although I have gotten some useful feedback on my patches of the above and will be incorporating that as I submit those patches for commit)
As an example of what compiles through this commit:
template <class F1, class F2>
struct overload : F1, F2 {
using F1::operator();
using F2::operator();
overload(F1 f1, F2 f2) : F1(f1), F2(f2) { }
};
auto Recursive = [](auto Self, auto h, auto ... rest) {
return 1 + Self(Self, rest...);
};
auto Base = [](auto Self, auto h) {
return 1;
};
overload<decltype(Base), decltype(Recursive)> O(Base, Recursive);
int num_params = O(O, 5, 3, "abc", 3.14, 'a');
Please see attached tests for more examples.
This patch has been reviewed by Doug and Richard. Minor changes (non-functionality affecting) have been made since both of them formally looked at it, but the changes involve removal of supernumerary return type deduction changes (since they are now redundant, with richard having committed a recent patch to address return type deduction for C++11 lambdas using C++14 semantics).
Some implementation notes:
- Add a new Declarator context => LambdaExprParameterContext to
clang::Declarator to allow the use of 'auto' in declaring generic
lambda parameters
- Add various helpers to CXXRecordDecl to facilitate identifying
and querying a closure class
- LambdaScopeInfo (which maintains the current lambda's Sema state)
was augmented to house the current depth of the template being
parsed (id est the Parser calls Sema::RecordParsingTemplateParameterDepth)
so that SemaType.cpp::ConvertDeclSpecToType may use it to immediately
generate a template-parameter-type when 'auto' is parsed in a generic
lambda parameter context. (i.e we do NOT use AutoType deduced to
a template parameter type - Richard seemed ok with this approach).
We encode that this template type was generated from an auto by simply
adding $auto to the name which can be used for better diagnostics if needed.
- SemaLambda.h was added to hold some common lambda utility
functions (this file is likely to grow ...)
- Teach Sema::ActOnStartOfFunctionDef to check whether it
is being called to instantiate a generic lambda's call
operator, and if so, push an appropriately prepared
LambdaScopeInfo object on the stack.
- various tests were added - but much more will be needed.
There is obviously more work to be done, and both Richard (weakly) and Doug (strongly)
have requested that LambdaExpr be removed form the CXXRecordDecl LambdaDefinitionaData
in a future patch which is forthcoming.
A greatful thanks to all reviewers including Eli Friedman, James Dennett,
and especially the two gracious wizards (Richard Smith and Doug Gregor)
who spent hours providing feedback (in person in Chicago and on the mailing lists).
And yet I am certain that I have allowed unidentified bugs to creep in; bugs, that I will do my best to slay, once identified!
Thanks!
llvm-svn: 191453
Specifically, the following features are not included in this commit:
- any sort of capturing within generic lambdas
- nested lambdas
- conversion operator for captureless lambdas
- ensuring all visitors are generic lambda aware
As an example of what compiles:
template <class F1, class F2>
struct overload : F1, F2 {
using F1::operator();
using F2::operator();
overload(F1 f1, F2 f2) : F1(f1), F2(f2) { }
};
auto Recursive = [](auto Self, auto h, auto ... rest) {
return 1 + Self(Self, rest...);
};
auto Base = [](auto Self, auto h) {
return 1;
};
overload<decltype(Base), decltype(Recursive)> O(Base, Recursive);
int num_params = O(O, 5, 3, "abc", 3.14, 'a');
Please see attached tests for more examples.
Some implementation notes:
- Add a new Declarator context => LambdaExprParameterContext to
clang::Declarator to allow the use of 'auto' in declaring generic
lambda parameters
- Augment AutoType's constructor (similar to how variadic
template-type-parameters ala TemplateTypeParmDecl are implemented) to
accept an IsParameterPack to encode a generic lambda parameter pack.
- Add various helpers to CXXRecordDecl to facilitate identifying
and querying a closure class
- LambdaScopeInfo (which maintains the current lambda's Sema state)
was augmented to house the current depth of the template being
parsed (id est the Parser calls Sema::RecordParsingTemplateParameterDepth)
so that Sema::ActOnLambdaAutoParameter may use it to create the
appropriate list of corresponding TemplateTypeParmDecl for each
auto parameter identified within the generic lambda (also stored
within the current LambdaScopeInfo). Additionally,
a TemplateParameterList data-member was added to hold the invented
TemplateParameterList AST node which will be much more useful
once we teach TreeTransform how to transform generic lambdas.
- SemaLambda.h was added to hold some common lambda utility
functions (this file is likely to grow ...)
- Teach Sema::ActOnStartOfFunctionDef to check whether it
is being called to instantiate a generic lambda's call
operator, and if so, push an appropriately prepared
LambdaScopeInfo object on the stack.
- Teach Sema::ActOnStartOfLambdaDefinition to set the
return type of a lambda without a trailing return type
to 'auto' in C++1y mode, and teach the return type
deduction machinery in SemaStmt.cpp to process either
C++11 and C++14 lambda's correctly depending on the flag.
- various tests were added - but much more will be needed.
A greatful thanks to all reviewers including Eli Friedman,
James Dennett and the ever illuminating Richard Smith. And
yet I am certain that I have allowed unidentified bugs to creep in;
bugs, that I will do my best to slay, once identified!
Thanks!
llvm-svn: 188977
Make sure we properly treat names defined inside a block as local
names. There are basically three fixes here. One, correctly
treat blocks as a context where we need to use local-name mangling using
the new isLocalContainerContext helper. Two, make
CXXNameMangler::manglePrefix handle local names in a consistent way.
Three, extend CXXNameMangler::mangleLocalName so it can mangle a block
correctly.
llvm-svn: 185450
This commit rearranges the logic in CXXNameMangler::mangleLocalName and
GetLocalClassDecl so that it doesn't accidentally skip over lambdas. It
also reduces code duplication a bit.
llvm-svn: 185402
Blocks, like lambdas, can be written in contexts which are required to be
treated as the same under ODR. Unlike lambdas, it isn't possible to actually
take the address of a block, so the mangling of the block itself doesn't
matter. However, objects like static variables inside a block do need to
be mangled in a consistent way.
There are basically three components here. One, block literals need a
consistent numbering. Two, objects/types inside a block literal need
to be mangled using it. Three, objects/types inside a block literal need
to have their linkage computed correctly.
llvm-svn: 185372
Faisal Vali