Note that this transformation has a substantial semantic effect outside of ARC: it gives the converted lambda lifetime semantics similar to a block literal. With ARC, the effect is much less obvious because the lifetime of blocks is already managed.
llvm-svn: 151797
block pointer that returns a block literal which captures (by copy)
the lambda closure itself. Some aspects of the block literal are left
unspecified, namely the capture variable (which doesn't actually
exist) and the body (which will be filled in by IRgen because it can't
be written as an AST).
Because we're switching to this model, this patch also eliminates
tracking the copy-initialization expression for the block capture of
the conversion function, since that information is now embedded in the
synthesized block literal. -1 side tables FTW.
llvm-svn: 151131
expression after we've finished the function body of the corresponding
function call operator. Otherwise, ActOnFinishFunctionBody() will see
the (unfinished) evaluation context of the lambda expression
itself. Fixes PR12031.
llvm-svn: 151082
arguments. There are two aspects to this:
- Make sure that when marking the declarations referenced in a
default argument, we don't try to mark local variables, both because
it's a waste of time and because the semantics are wrong: we're not
in a place where we could capture these variables again even if it
did make sense.
- When a lambda expression occurs in a default argument of a
function template, make sure that the corresponding closure type is
considered dependent, so that it will get properly instantiated. The
second bit is a bit of a hack; to fix it properly, we may have to
rearchitect our handling of default arguments, parsing them only
after creating the function definition. However, I'd like to
separate that work from the lambdas work.
llvm-svn: 151076
stable mangling, since these lambdas can end up in multiple
translation units. Sema is responsible for deciding when this is the
case, because it's already responsible for choosing the mangling
number.
llvm-svn: 151029
default arguments of function parameters. This simple-sounding task is
complicated greatly by two issues:
(1) Default arguments aren't actually a real context, so we need to
maintain extra state within lambda expressions to track when a
lambda was actually in a default argument.
(2) At the time that we parse a default argument, the FunctionDecl
doesn't exist yet, so lambda closure types end up in the enclosing
context. It's not clear that we ever want to change that, so instead
we introduce the notion of the "effective" context of a declaration
for the purposes of name mangling.
llvm-svn: 151011
and introducing the lambda closure type and its function call
operator. Previously, we assumed that the lambda closure type would
land directly in the current context, and not some parent context (as
occurs with linkage specifications). Thanks to Richard for the test case.
llvm-svn: 150987
name mangling in the Itanium C++ ABI for lambda expressions is so
dependent on context, we encode the number used to encode each lambda
as part of the lambda closure type, and maintain this value within
Sema.
Note that there are a several pieces still missing:
- We still get the linkage of lambda expressions wrong
- We aren't properly numbering or mangling lambda expressions that
occur in default function arguments or in data member initializers.
- We aren't (de-)serializing the lambda numbering tables
llvm-svn: 150982
eliminating a bunch of redundant code and properly modeling how the
captures of outside blocks/lambdas affect the types seen by inner
captures.
This new scheme makes two passes over the capturing scope stack. The
first pass goes up the stack (from innermost to outermost), assessing
whether the capture looks feasible and stopping when it either hits
the scope where the variable is declared or when it finds an existing
capture. The second pass then walks down the stack (from outermost to
innermost), capturing the variable at each step and updating the
captured type and the type that an expression referring to that
captured variable would see. It also checks type-specific
restrictions, such as the inability to capture an array within a
block. Note that only the first odr-use of each
variable needs to do the full walk; subsequent uses will find the
capture immediately, so multiple walks need not occur.
The same routine that builds the captures can also compute the type of
the captures without signaling errors and without actually performing
the capture. This functionality is used to determine the type of
declaration references as well as implementing the weird decltype((x))
rule within lambda expressions.
The capture code now explicitly takes sides in the debate over C++
core issue 1249, which concerns the type of captures within nested
lambdas. We opt to use the more permissive, more useful definition
implemented by GCC rather than the one implemented by EDG.
llvm-svn: 150875
conversion to function pointer. Rather than having IRgen synthesize
the body of this function, we instead introduce a static member
function "__invoke" with the same signature as the lambda's
operator() in the AST. Sema then generates a body for the conversion
to function pointer which simply returns the address of __invoke. This
approach makes it easier to evaluate a call to the conversion function
as a constant, makes the linkage of the __invoke function follow the
normal rules for member functions, and may make life easier down the
road if we ever want to constexpr'ify some of lambdas.
Note that IR generation is responsible for filling in the body of
__invoke (Sema just adds a dummy body), because the body can't
generally be expressed in C++.
Eli, please review!
llvm-svn: 150783
lambda expressions. Because these issue was pulled back from Ready
status at the Kona meeting, we still emit an ExtWarn when using
default arguments for lambda expressions.
llvm-svn: 150519
expression with the original call operator, so that we don't try to
separately instantiate the call operator. Test and tweak a few more
bits for template instantiation of lambda expressions.
llvm-svn: 150440
expressions. This is mostly a simple refact, splitting the main "start
a lambda expression" function into smaller chunks that are driven
either from the parser (Sema::ActOnLambdaExpr) or during AST
transformation (TreeTransform::TransformLambdaExpr). A few minor
interesting points:
- Added new entry points for TreeTransform, so that we can
explicitly establish the link between the lambda closure type in the
template and the lambda closure type in the instantiation.
- Added a bit into LambdaExpr specifying whether it had an explicit
result type or not. We should have had this anyway.
This code is 'lightly' tested.
llvm-svn: 150417
LambdaExpr over to the CXXRecordDecl. This allows us to eliminate the
back-link from the closure type to the LambdaExpr, which will simplify
and lazify AST deserialization.
llvm-svn: 150393
default is '=', and reword the warning about explicitly capturing
'this' in such lambdas to indicate that only explicit capture is
banned.
Introduce Fix-Its for this and other "save the programmer from
themself" rules regarding what can be explicitly captured and what
must be implicitly captured.
llvm-svn: 150256
have finished parsing the body, so that name lookup will never find
anything within the closure type. Then, add this operator() and the
conversion function (if available) before completing the class.
llvm-svn: 150252
to pretty-print such function types better, and to fix a case where we were not
instantiating templates in lexical order. In passing, move the Variadic bit from
Type's bitfields to FunctionProtoType to get the Type bitfields down to 32 bits.
Also ensure that we always substitute the return type of a function when
substituting explicitly-specified arguments, since that can cause us to bail
out with a SFINAE error before we hit a hard error in parameter substitution.
llvm-svn: 150241
[expr.prim.lambda]p4, including the current suggested resolution of
core isue 975, which allows multiple return statements so long as the
types match. ExtWarn when user code is actually making use of this
extension.
llvm-svn: 150168
function call operator (to the lambda class). This allows us to IRgen
calls to simple (non-capturing) lambdas, e.g.,
[](int i, int j) -> int { return i + j; }(1, 2)
Eli will be providing test cases as he brings up more IRgen.
llvm-svn: 150166
- Complete the lambda class when we finish the lambda expression
(previously, it was left in the "being completed" state)
- Actually return the LambdaExpr object and bind to the resulting
temporary when needed.
- Detect when cleanups are needed while capturing a variable into a
lambda (e.g., due to default arguments in the copy constructor), and
make sure those cleanups apply for the whole of the lambda
expression.
llvm-svn: 150123
Eli Friedman