Create a header and impl file for the structural equivalence context.
This is to allow other users outside clang importer. NFCI
Differential Revision: https://reviews.llvm.org/D31777
rdar://problem/30167717
llvm-svn: 301604
When the SearchName is already calculated we should use that for the lookup.
Patch by Peter Szecsi!
Differential Revision: https://reviews.llvm.org/D30877
llvm-svn: 299354
Sema holds the current FPOptions which is adjusted by 'pragma STDC
FP_CONTRACT'. This then gets propagated into expression nodes as they are
built.
This encapsulates FPOptions so that this propagation happens opaquely rather
than directly with the fp_contractable on/off bit. This allows controlled
transitioning of fp_contractable to a ternary value (off, on, fast). It will
also allow adding more fast-math flags later.
This is toward moving fp-contraction=fast from an LLVM TargetOption to a
FastMathFlag in order to fix PR25721.
Differential Revision: https://reviews.llvm.org/D31166
llvm-svn: 298877
This enhances the AST to keep track of locations of the names in those ObjC property attributes, and reports them for indexing.
Patch by Nathan Hawes!
https://reviews.llvm.org/D30907
llvm-svn: 297972
Essentially, as a base class constructor does not construct virtual bases, such
a constructor for an abstract class does not need the corresponding base class
construction to be valid, and likewise for destructors.
This creates an awkward situation: clang will sometimes generate references to
the complete object and deleting destructors for an abstract class (it puts
them in the construction vtable for a derived class). But we can't generate a
"correct" version of these because we can't generate references to base class
constructors any more (if they're template specializations, say, we might not
have instantiated them and can't assume any other TU will emit a copy).
Fortunately, we don't need to, since no correct program can ever invoke them,
so instead emit symbols that just trap.
We should stop emitting references to these symbols, but still need to emit
definitions for compatibility.
llvm-svn: 296275
We model deduction-guides as functions with a new kind of name that identifies
the template whose deduction they guide; the bulk of this patch is adding the
new name kind. This gives us a clean way to attach an extensible list of guides
to a class template in a way that doesn't require any special handling in AST
files etc (and we're going to need these functions we come to performing
deduction).
llvm-svn: 294266
This change adds a new type node, DeducedTemplateSpecializationType, to
represent a type template name that has been used as a type. This is modeled
around AutoType, and shares a common base class for representing a deduced
placeholder type.
We allow deduced class template types in a few more places than the standard
does: in conditions and for-range-declarators, and in new-type-ids. This is
consistent with GCC and with discussion on the core reflector. This patch
does not yet support deduced class template types being named in typename
specifiers.
llvm-svn: 293207
* Support template partial specialization
* Avoid infinite recursion in IsStructurallyEquivalent for TemplateArgument with implementing IsStructurallyEquivalent for TemplateName
llvm-svn: 292776
Fixes a crash in modules where the template class decl becomes the most recent
decl in the redeclaration chain and forcing the template instantiator try to
instantiate the friend declaration, rather than the template definition.
In practice, A::list<int> produces a TemplateSpecializationType
A::__1::list<int, allocator<type-parameter-0-0> >' failing to replace to
subsitute the default argument to allocator<int>.
Kudos Richard Smith (D28399).
llvm-svn: 291753
copy constructors of classes with array members, instead using
ArrayInitLoopExpr to represent the initialization loop.
This exposed a bug in the static analyzer where it was unable to differentiate
between zero-initialized and unknown array values, which has also been fixed
here.
llvm-svn: 289618
expansions by calling getSpellingLoc(). That's great in most cases, but for
macros defined in the '<built-in>' source file, the source file is invalid
and does not import correctly, causing an assertion failure (the assertion
is Invalid SLocOffset or bad function choice).
A more reliable way to avoid this is to use getFileLoc(), which does not
return built-in locations. This avoids the crash but still preserves valid
source locations.
I've added a testcase that covers the previously crashing scenario.
https://reviews.llvm.org/D26054
llvm-svn: 286144
We also need to add ObjCTypeParamTypeLoc. ObjCTypeParamType supports the
representation of "T <protocol>" where T is a type parameter. Before this,
we use TypedefType to represent the type parameter for ObjC.
ObjCTypeParamType has "ObjCTypeParamDecl *OTPDecl" and it extends from
ObjCProtocolQualifiers. It is a non-canonical type and is canonicalized
to the underlying type with the protocol qualifiers.
rdar://24619481
rdar://25060179
Differential Revision: http://reviews.llvm.org/D23079
llvm-svn: 281355
Summary:
Space for storing the //constraint-expression// of the
//requires-clause// associated with a `TemplateParameterList` is
arranged by taking a bit out of the `NumParams` field for the purpose
of determining whether there is a //requires-clause// or not, and by
adding to the trailing objects tied to the `TemplateParameterList`. An
accessor is provided.
An appropriate argument is supplied to `TemplateParameterList::Create`
at the various call sites.
Serialization changes will addressed as the Concepts implementation
becomes more solid.
Drive-by fix:
This change also replaces the custom
`FixedSizeTemplateParameterListStorage` implementation with one that
follows the interface provided by `llvm::TrailingObjects`.
Reviewers: aaron.ballman, faisalv, rsmith
Subscribers: cfe-commits, nwilson
Differential Revision: https://reviews.llvm.org/D19322
llvm-svn: 276069
distinct anonymous structs remain distinct despite having similar layout.
This is already ensured by distinguishing based on their placement in the parent
struct, using the function `findAnonymousStructOrUnionIndex`.
The problem is that this function only handles anonymous structs, like
```
class Foo { struct { int a; } }
```
and not untagged structs like
```
class Foo { struct { int a; } var; }
```
Both need to be handled, and this patch fixes that. The test case ensures that this functionality doesn't regress.
Thanks to Manman Ren for review.
https://reviews.llvm.org/D22270
llvm-svn: 275460
Also added named casts and propagation of "implicit" to fix the LLDB testsuite.
This is a fixed commit of r269546, which was reverted by r269575.
Thanks to Aleksei Sidorin for review and advice.
llvm-svn: 269693
IdentifierInfos are assigned builtin IDs during parsing, but Idents.get() does
not do that work. So the ASTImporter needs to additionally set the builtin ID
for the newly-created IdentifierInfo. This patch does that.
Currently ASTMerge tests only check syntax and the ASTMatchers don't check for
builtin IDs, so this is tricky to test, but LLDB will have a test for this.
llvm-svn: 269553
Every class as parsed by Clang has a forward declaration of itself as a member:
class A {
class A;
...
}
but when the parser generates this it ensures that the RecordTypes for the two
are the same. This makes (among other things) inheritance work. This patch
fixes a bug where the ASTImporter generated two separate RecordTypes when
importing the class and the contained forward declaration, and adds a test case.
Thanks to Doug Gregor for advice on this.
llvm-svn: 269551
a base class via a using-declaration. If a class has a using-declaration
declaring either a constructor or an assignment operator, eagerly declare its
special members in case they need to displace a shadow declaration from a
using-declaration.
llvm-svn: 269398
This is in preparation for C++ P0136R1, which switches the model for inheriting
constructors over from synthesizing a constructor to finding base class
constructors (via using shadow decls) when looking for derived class
constructors.
llvm-svn: 269231
Putting OpenCLImageTypes.def to clangAST library violates layering requirement: "It's not OK for a Basic/ header to include an AST/ header".
This fixes the modules build.
Differential revision: http://reviews.llvm.org/D18954
Reviewers: Richard Smith, Vassil Vassilev.
llvm-svn: 266180
I. Current implementation of images is not conformant to spec in the following points:
1. It makes no distinction with respect to access qualifiers and therefore allows to use images with different access type interchangeably. The following code would compile just fine:
void write_image(write_only image2d_t img);
kernel void foo(read_only image2d_t img) { write_image(img); } // Accepted code
which is disallowed according to s6.13.14.
2. It discards access qualifier on generated code, which leads to generated code for the above example:
call void @write_image(%opencl.image2d_t* %img);
In OpenCL2.0 however we can have different calls into write_image with read_only and wite_only images.
Also generally following compiler steps have no easy way to take different path depending on the image access: linking to the right implementation of image types, performing IR opts and backend codegen differently.
3. Image types are language keywords and can't be redeclared s6.1.9, which can happen currently as they are just typedef names.
4. Default access qualifier read_only is to be added if not provided explicitly.
II. This patch corrects the above points as follows:
1. All images are encapsulated into a separate .def file that is inserted in different points where image handling is required. This avoid a lot of code repetition as all images are handled the same way in the code with no distinction of their exact type.
2. The Cartesian product of image types and image access qualifiers is added to the builtin types. This simplifies a lot handling of access type mismatch as no operations are allowed by default on distinct Builtin types. Also spec intended access qualifier as special type qualifier that are combined with an image type to form a distinct type (see statement above - images can't be created w/o access qualifiers).
3. Improves testing of images in Clang.
Author: Anastasia Stulova
Reviewers: bader, mgrang.
Subscribers: pxli168, pekka.jaaskelainen, yaxunl.
Differential Revision: http://reviews.llvm.org/D17821
llvm-svn: 265783
The testcase for this is in LLDB, adeed by r264662.
This patch adds support for a variety of new expression types to the AST
importer, mostly related to C++. It also adds support for importing lambdas
correctly, and adds support for importing the attributes attached to any Decl.
Finally, the patch adds a new templated function to ASTNodeImporter that imports
arbitrary arrays of importable things into a bump-allocated array attached to
getToContext(). This is a pattern we see at many places in ASTNodeImporter;
rather than do it slightly differently at each point, this function does it one
way.
<rdar://problem/22864976>
llvm-svn: 264669
I should have checked and imported D's in-class initializer.
Instead I accidentally used ToField's in-class initializer,
which is always NULL so ToField will never get one.
<rdar://problem/24943405>
llvm-svn: 262576
Previously, the ASTImporter, when copying a FieldDecl, would make the
new FieldDecl use the exact same in-class initializer as the original
FieldDecl, which is a problem since the initializer is in the wrong AST.
The initializer must be imported, just like all the other parts of the
field.
Doug Gregor reviewed this fix.
<rdar://problem/24943405>
llvm-svn: 262572
r261297 called hasUserProvidedDefaultConstructor() to check if defining a
const object is ok. This is incorrect for this example:
struct X { template<typename ...T> X(T...); int n; };
const X x; // formerly OK, now bogus error
Instead, track if a class has a defaulted default constructor, and disallow
a const object for classes that either have defaulted default constructors or
if they need an implicit constructor.
Bug report and fix approach by Richard Smith, thanks!
llvm-svn: 261770
C++11 requires const objects to have a user-provided constructor, even for
classes without any fields. DR 253 relaxes this to say "If the implicit default
constructor initializes all subobjects, no initializer should be required."
clang is currently the only compiler that implements this C++11 rule, and e.g.
libstdc++ relies on something like DR 253 to compile in newer versions. This
change makes it possible to build code that says `const vector<int> v;' again
when using libstdc++5.2 and _GLIBCXX_DEBUG
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60284).
Fixes PR23381.
http://reviews.llvm.org/D16552
llvm-svn: 261297
Add "enum ObjCPropertyQueryKind" to a few APIs that used to only take the name
of the property: ObjCPropertyDecl::findPropertyDecl,
ObjCContainerDecl::FindPropertyDeclaration,
ObjCInterfaceDecl::FindPropertyVisibleInPrimaryClass,
ObjCImplDecl::FindPropertyImplDecl, and Sema::ActOnPropertyImplDecl.
ObjCPropertyQueryKind currently has 3 values:
OBJC_PR_query_unknown, OBJC_PR_query_instance, OBJC_PR_query_class
This extra parameter specifies that we are looking for an instance property with
the given name, or a class property with the given name, or any property with
the given name (if both exist, the instance property will be returned).
rdar://23891898
llvm-svn: 259070
Summary:
Support for OpenCL 2.0 pipe type.
This is a bug-fix version for bader's patch reviews.llvm.org/D14441
Reviewers: pekka.jaaskelainen, Anastasia
Subscribers: bader, Anastasia, cfe-commits
Differential Revision: http://reviews.llvm.org/D15603
llvm-svn: 257254
https://gcc.gnu.org/onlinedocs/gcc/Typeof.html
Differences from the GCC extension:
* __auto_type is also permitted in C++ (but only in places where
it could appear in C), allowing its use in headers that might
be shared across C and C++, or used from C++98
* __auto_type can be combined with a declarator, as with C++ auto
(for instance, "__auto_type *p")
* multiple variables can be declared in a single __auto_type
declaration, with the C++ semantics (the deduced type must be
the same in each case)
This patch also adds a missing restriction on applying typeof to
a bit-field, which GCC has historically rejected in C (due to
lack of clarity as to whether the operand should be promoted).
The same restriction also applies to __auto_type in C (in both
GCC and Clang).
This also fixes PR25449.
Patch by Nicholas Allegra!
llvm-svn: 252690
Summary: It breaks the build for the ASTMatchers
Subscribers: klimek, cfe-commits
Differential Revision: http://reviews.llvm.org/D13893
llvm-svn: 250827
when importing type parameter lists. The reason is that type parameters
have their DeclContexts set to the interface that is parameterized with those
types, and the importer would follow that loop and blow the stack out.
I've changed the way this works so that the type parameters are only imported
after the interface that contains them has been registered via the Imported()
function.
This is tested by LLDB.
<rdar://problem/20315663>
llvm-svn: 241556
Introduce co- and contra-variance for Objective-C type parameters,
which allows us to express that (for example) an NSArray is covariant
in its type parameter. This means that NSArray<NSMutableString *> * is
a subtype of NSArray<NSString *> *, which is expected of the immutable
Foundation collections.
Type parameters can be annotated with __covariant or __contravariant
to make them co- or contra-variant, respectively. This feature can be
detected by __has_feature(objc_generics_variance). Implements
rdar://problem/20217490.
llvm-svn: 241549
The __kindof type qualifier can be applied to Objective-C object
(pointer) types to indicate id-like behavior, which includes implicit
"downcasting" of __kindof types to subclasses and id-like message-send
behavior. __kindof types provide better type bounds for substitutions
into unspecified generic types, which preserves more type information.
llvm-svn: 241548
When messaging a method that was defined in an Objective-C class (or
category or extension thereof) that has type parameters, substitute
the type arguments for those type parameters. Similarly, substitute
into property accesses, instance variables, and other references.
This includes general infrastructure for substituting the type
arguments associated with an ObjCObject(Pointer)Type into a type
referenced within a particular context, handling all of the
substitutions required to deal with (e.g.) inheritance involving
parameterized classes. In cases where no type arguments are available
(e.g., because we're messaging via some unspecialized type, id, etc.),
we substitute in the type bounds for the type parameters instead.
Example:
@interface NSSet<T : id<NSCopying>> : NSObject <NSCopying>
- (T)firstObject;
@end
void f(NSSet<NSString *> *stringSet, NSSet *anySet) {
[stringSet firstObject]; // produces NSString*
[anySet firstObject]; // produces id<NSCopying> (the bound)
}
When substituting for the type parameters given an unspecialized
context (i.e., no specific type arguments were given), substituting
the type bounds unconditionally produces type signatures that are too
strong compared to the pre-generics signatures. Instead, use the
following rule:
- In covariant positions, such as method return types, replace type
parameters with “id” or “Class” (the latter only when the type
parameter bound is “Class” or qualified class, e.g,
“Class<NSCopying>”)
- In other positions (e.g., parameter types), replace type
parameters with their type bounds.
- When a specialized Objective-C object or object pointer type
contains a type parameter in its type arguments (e.g.,
NSArray<T>*, but not NSArray<NSString *> *), replace the entire
object/object pointer type with its unspecialized version (e.g.,
NSArray *).
llvm-svn: 241543
Objective-C type arguments can be provided in angle brackets following
an Objective-C interface type. Syntactically, this is the same
position as one would provide protocol qualifiers (e.g.,
id<NSCopying>), so parse both together and let Sema sort out the
ambiguous cases. This applies both when parsing types and when parsing
the superclass of an Objective-C class, which can now be a specialized
type (e.g., NSMutableArray<T> inherits from NSArray<T>).
Check Objective-C type arguments against the type parameters of the
corresponding class. Verify the length of the type argument list and
that each type argument satisfies the corresponding bound.
Specializations of parameterized Objective-C classes are represented
in the type system as distinct types. Both specialized types (e.g.,
NSArray<NSString *> *) and unspecialized types (NSArray *) are
represented, separately.
llvm-svn: 241542
Produce type parameter declarations for Objective-C type parameters,
and attach lists of type parameters to Objective-C classes,
categories, forward declarations, and extensions as
appropriate. Perform semantic analysis of type bounds for type
parameters, both in isolation and across classes/categories/extensions
to ensure consistency.
Also handle (de-)serialization of Objective-C type parameter lists,
along with sundry other things one must do to add a new declaration to
Clang.
Note that Objective-C type parameters are typedef name declarations,
like typedefs and C++11 type aliases, in support of type erasure.
Part of rdar://problem/6294649.
llvm-svn: 241541
The patch is generated using this command:
$ tools/extra/clang-tidy/tool/run-clang-tidy.py -fix \
-checks=-*,llvm-namespace-comment -header-filter='llvm/.*|clang/.*' \
work/llvm/tools/clang
To reduce churn, not touching namespaces spanning less than 10 lines.
llvm-svn: 240270
Introduce context-sensitive, non-underscored nullability specifiers
(nonnull, nullable, null_unspecified) for Objective-C method return
types, method parameter types, and properties.
Introduce Objective-C-specific semantics, including computation of the
nullability of the result of a message send, merging of nullability
information from the @interface of a class into its @implementation,
etc .
This is the Objective-C part of rdar://problem/18868820.
llvm-svn: 240154
a FileID corresponds to a real file or to a
memory buffer. The old method didn't work when
Clang was built Release, which meant it wasn't
a very good method at all.
llvm-svn: 236188
some bugs in the ASTImporter that this exposed:
- When importing functions, the body (if any) was
previously ignored. This patch ensures that the
body is imported also.
- When a function-local Decl is imported, the first
thing the ASTImporter does is import its context
(via ImportDeclParts()). This can trigger
importing the Decl again as part of the body of
the function (but only once, since the function's
Decl has been added to ImportedDecls). This patch
fixes that problem by extending ImportDeclParts()
to return the imported Decl if it was imported as
part of importing its context, and the patch adds
ASTImporter::GetAlreadyImportedOrNull() to support
this query. All callers of ImportDeclParts return
the imported version of the Decl if ImportDeclParts()
returns it.
- When creating functions, InnerLocStart of the source
function was re-used without importing. This is a
straight up bug, and this patch makes ASTImporter
import the InnerLocStart and use the imported version.
- When importing FileIDs, the ASTImporter previously
always tried to re-load the file for the corresponding
CacheEntry from disk. This doesn't work if the
CacheEntry corresponds to a named memory buffer. This
patch changes the code so that if the UniqueID for the
cache entry is invalid (i.e., it is not a disk file)
the whole entry is treated as if it were invalid, which
forces an in-memory copy of the buffer.
Also added test cases, using the new support committed in
236011.
llvm-svn: 236012
Bitfield RefersToEnclosingLocal of Stmt::DeclRefExprBitfields renamed to RefersToCapturedVariable to reflect latest changes introduced in commit 224323. Also renamed method Expr::refersToEnclosingLocal() to Expr::refersToCapturedVariable() and comments for constant arguments.
No functional changes.
llvm-svn: 224329
To ensure that we don't import duplicates, the ASTImporter often
checks the DeclContext for a Decl before importing it to see if
a Decl with the same name is already present.
This is problematic if the Decl is inside a transparent context
like an extern "C" block. Lookup isn't allowed on such contexts,
and in fact they assert() if you do that. So instead we look at
the redeclaration context -- the containing context that can be
used safely for these kinds of checks -- instead.
llvm-svn: 223912
SourceLocations. LLDB rarely has the same files
mapped into the target AST context as the source
AST context, so the ASTImporter shouldn't expect
to see those files there.
This started to become a problem when importing
entities from modules -- these have proper source
locations, in contrast to all the ASTs LLDB
creates which have empty ones.
llvm-svn: 223900
LinkageSpecDecls. This is relevant when LLDB
wants to import Decls from non-C++ modules,
since many declarations are in extern "C"
blocks.
llvm-svn: 223860
It's not clear how this would be tested - I imagine we should have an
ASTImporter test that RAVs the new AST and checks that all the elements
in it are from this ASTContext and not the foreign one... but I know
little about the ASTImporter and how/where that testing might be done.
(post-commit review feedback from Richard Smith on r219900)
llvm-svn: 220411
Plumb through the full QualType of the TemplateArgument::Declaration, as
it's insufficient to only know whether the type is a reference or
pointer (that was necessary for mangling, but insufficient for debug
info). This shouldn't increase the size of TemplateArgument as
TemplateArgument::Integer is still longer by another 32 bits.
Several bits of code were testing that the reference-ness of the
parameters matched, but this seemed to be insufficient (various other
features of the type could've mismatched and wouldn't've been caught)
and unnecessary, at least insofar as removing those tests didn't cause
anything to fail.
(Richard - perchaps you can hypothesize why any of these checks might
need to test reference-ness of the parameters (& explain why
reference-ness is part of the mangling - I would've figured that for the
reference-ness to be different, a prior template argument would have to
be different). I'd be happy to add them in/beef them up and add test
cases if there's a reason for them)
llvm-svn: 219900
We build a NestedNameSpecifier that records the CXXRecordDecl in which
__super appeared. Name lookup is performed in all base classes of the
recorded CXXRecordDecl. Use of __super is allowed only inside class and
member function scope.
llvm-svn: 218484
FunctionProtoType::ExtProtoInfo. Most of the users of these fields don't care
about the other ExtProtoInfo bits and just want to talk about the exception
specification.
llvm-svn: 214450
anonymous structs to the same Decl in the
ASTImporter, ensure that both are filled in
from their external sources (if present).
Otherwise two different structs may be
identified erroneously.
llvm-svn: 202869
A return type is the declared or deduced part of the function type specified in
the declaration.
A result type is the (potentially adjusted) type of the value of an expression
that calls the function.
Rule of thumb:
* Declarations have return types and parameters.
* Expressions have result types and arguments.
llvm-svn: 200082
Fix a perennial source of confusion in the clang type system: Declarations and
function prototypes have parameters to which arguments are supplied, so calling
these 'arguments' was a stretch even in C mode, let alone C++ where default
arguments, templates and overloading make the distinction important to get
right.
Readability win across the board, especially in the casting, ADL and
overloading implementations which make a lot more sense at a glance now.
Will keep an eye on the builders and update dependent projects shortly.
No functional change.
llvm-svn: 199686
- Remove the additions to ObjCMethodDecl & ObjCIVarDecl that were getting de/serialized and consolidate
all functionality for the checking for this warning in Sema::DiagnoseUnusedBackingIvarInAccessor
- Don't check immediately after the method body is finished, check when the @implementation is finished.
This is so we can see if the ivar was referenced by any other method, even if the method was defined after the accessor.
- Don't silence the warning if any method is called from the accessor silence it if the accessor delegates to another method via self.
rdar://15727325
llvm-svn: 198432
more than one such initializer in a union, make mem-initializers override
default initializers for other union members, handle anonymous unions with
anonymous struct members better. Fix a couple of semi-related bugs exposed by
the tests for same.
llvm-svn: 196892
Summary:
In general, this type node can be used to represent any type adjustment
that occurs implicitly without losing type sugar. The immediate use of
this is to adjust the calling conventions of member function pointer
types without breaking template instantiation.
Fixes PR17996.
Reviewers: rsmith
Differential Revision: http://llvm-reviews.chandlerc.com/D2332
llvm-svn: 196451
would be deleted are still declared, but are ignored by overload resolution.
Also, don't delete such members if a subobject has no corresponding move
operation and a non-trivial copy. This causes us to implicitly declare move
operations in more cases, but risks move-assigning virtual bases multiple
times in some circumstances (a warning for that is to follow).
llvm-svn: 193969
ASTImporter when importing the following types:
typedef struct {
} A;
typedef struct {
A a;
} B;
Suppose we have imported B, but we did not at that
time need to complete it. Then later we want to
import A. The struct is anonymous, so the first
thing we want to do is make sure no other anonymous
struct already matches it. So we set up an
StructuralEquivalenceContext and compare B with A.
This happens at ASTImporter.cpp:2179.
Now, in this scenario, B is not complete. So we go
and import its fields, including a, which causes A
to be imported. The ASTImporter doesn’t yet have A
in its list of already-imported things, so we
import A.
After the StructuralEquivalenceContext is finished
determining that A and B are different, the
ASTImporter concludes that A must be imported
because no equivalent exists, so it imports a second
copy of A. Now we have two different structs
representing A. This is really bad news.
The patch allows the StructuralEquivalenceContext to
use the original version of B when making its
comparison, obviating the need for an import and
cutting this loop.
llvm-svn: 192324
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
The goal of this sugar node is to be able to look at an arbitrary
FunctionType and tell if any of the parameters were decayed from an
array or function type. Ultimately this is necessary to implement
Microsoft's C++ name mangling scheme, which mangles decayed arrays
differently from normal pointers.
Reviewers: rsmith
Differential Revision: http://llvm-reviews.chandlerc.com/D1014
llvm-svn: 184763
The most common (non-buggy) case are where such objects are used as
return expressions in bool-returning functions or as boolean function
arguments. In those cases I've used (& added if necessary) a named
function to provide the equivalent (or sometimes negative, depending on
convenient wording) test.
DiagnosticBuilder kept its implicit conversion operator owing to the
prevalent use of it in return statements.
One bug was found in ExprConstant.cpp involving a comparison of two
PointerUnions (PointerUnion did not previously have an operator==, so
instead both operands were converted to bool & then compared). A test
is included in test/SemaCXX/constant-expression-cxx1y.cpp for the fix
(adding operator== to PointerUnion in LLVM).
llvm-svn: 181869
This patch renames getLinkage to getLinkageInternal. Only code that
needs to handle UniqueExternalLinkage specially should call this.
Linkage, as defined in the c++ standard, is provided by
getFormalLinkage. It maps UniqueExternalLinkage to ExternalLinkage.
Most places in the compiler actually want isExternallyVisible, which
handles UniqueExternalLinkage as internal.
llvm-svn: 181677
structs are compatible, check whether the fields
of the structs have the same name. This prevents
erroneous coalescing of (in particular) anonymous
structs.
llvm-svn: 180644
http://lab.llvm.org:8011/builders/clang-x86_64-darwin10-gdb went back green
before it processed the reverted 178663, so it could not have been the culprit.
Revert "Revert 178663."
This reverts commit 4f8a3eb2ce5d4ba422483439e20c8cbb4d953a41.
llvm-svn: 178682
For variables and functions clang used to store two storage classes. The one
"as written" in the code and a patched one, which, for example, propagates
static to the following decls.
This apparently is from the days clang lacked linkage computation. It is now
redundant and this patch removes it.
llvm-svn: 178663
consider (sub)module visibility.
The bulk of this change replaces myriad hand-rolled loops over the
linked list of Objective-C categories/extensions attached to an
interface declaration with loops using one of the four new category
iterator kinds:
visible_categories_iterator: Iterates over all visible categories
and extensions, hiding any that have their "hidden" bit set. This is
by far the most commonly used iterator.
known_categories_iterator: Iterates over all categories and
extensions, ignoring the "hidden" bit. This tends to be used for
redeclaration-like traversals.
visible_extensions_iterator: Iterates over all visible extensions,
hiding any that have their "hidden" bit set.
known_extensions_iterator: Iterates over all extensions, whether
they are visible to normal name lookup or not.
The effect of this change is that any uses of the visible_ iterators
will respect module-import visibility. See the new tests for examples.
Note that the old accessors for categories and extensions are gone;
there are *Raw() forms for some of them, for those (few) areas of the
compiler that have to manipulate the linked list of categories
directly. This is generally discouraged.
Part two of <rdar://problem/10634711>.
llvm-svn: 172665
produce a note for that diagnostic either with a different DiagnosticEngine or
after calling DiagnosticEngine::Reset(). That didn't make any sense, and did the
wrong thing if the original diagnostic was suppressed.
llvm-svn: 170636
the cases where we can't determine whether special members would be trivial
while building the class, we eagerly declare those special members. The impact
of this is bounded, since it does not trigger implicit declarations of special
members in classes which merely *use* those classes.
In order to determine whether we need to apply this rule, we also need to
eagerly declare move operations and destructors in cases where they might be
deleted. If a move operation were supposed to be deleted, it would instead
be suppressed, and we could need overload resolution to determine if we fall
back to a trivial copy operation. If a destructor were implicitly deleted,
it would cause the move constructor of any derived classes to be suppressed.
As discussed on cxx-abi-dev, C++11's selected constructor rules are also
retroactively applied as a defect resolution in C++03 mode, in order to
identify that class B has a non-trivial copy constructor (since it calls
A's constructor template, not A's copy constructor):
struct A { template<typename T> A(T &); };
struct B { mutable A a; };
llvm-svn: 169673
properly, rather than faking it up by pretending that a reference member makes
the default constructor non-trivial. That leads to rejects-valids when putting
such types inside unions.
llvm-svn: 169662
uncovered.
This required manually correcting all of the incorrect main-module
headers I could find, and running the new llvm/utils/sort_includes.py
script over the files.
I also manually added quite a few missing headers that were uncovered by
shuffling the order or moving headers up to be main-module-headers.
llvm-svn: 169237
constructor/assignment operator with a const-qualified parameter type. The
prior method for determining this incorrectly used overload resolution.
llvm-svn: 168775
only actually get the answer right if there was only a single
anonymous struct/union at that level. This is part of
<rdar://problem/11904570>; the test will go into LLDB itself.
llvm-svn: 166781
This more accurately reflects its use: this flag is set when a method
matches the getter or setter name for a property in the same class,
and does not actually specify whether or not the definition of the method
will be synthesized (either implicitly or explicitly with @synthesize).
This renames the setter and backing field as well, and changes the
(soon-to-be-obsolete?) XML dump format to use 'property_accessor'
instead of 'synthesized'.
llvm-svn: 165626
Clang will now honor the FP_CONTRACT pragma and emit LLVM
fmuladd intrinsics for expressions of the form A * B + C (when they occur in a
single statement).
llvm-svn: 164989
enough information so we can mangle them correctly in cases involving
dependent parameter types. (This specifically impacts cases involving
null pointers and cases involving parameters of reference type.)
Fix the mangler to use this information instead of trying to scavenge
it out of the parameter declaration.
<rdar://problem/12296776>.
llvm-svn: 164656
FunctionDecl that we are importing the FunctionProtoType for, in which case we'll have
infinite recursion when importing.
Initially create a FunctionProtoType with null ExceptionSpecDecl/ExceptionSpecTemplate and
update the type in ASTNodeImporter::VisitFunctionDecl after the FunctionDecl has been created.
llvm-svn: 164450
We need an efficient mechanism to determine whether a defaulted default
constructor is constexpr, in order to determine whether a class is a literal
type, so keep the incrementally-built form on CXXRecordDecl. Remove the
on-demand computation of same, so that we only have one method for determining
whether a default constructor is constexpr. This doesn't affect correctness,
since default constructor lookup is much simpler than selecting a constructor
for copying or moving.
We don't need a corresponding mechanism for defaulted copy or move constructors,
since they can't affect whether a type is a literal type. Conversely, checking
whether such functions are constexpr can require non-trivial effort, so we defer
such checks until the copy or move constructor is required.
Thus we now only compute whether a copy or move constructor is constexpr on
demand, and only compute whether a default constructor is constexpr in advance.
This is unfortunate, but seems like the best solution.
llvm-svn: 158290
The integral APSInt value is now stored in a decomposed form and the backing
store for large values is allocated via the ASTContext. This way its not
leaked as TemplateArguments are never destructed when they are allocated in
the ASTContext. Since the integral data is immutable it is now shared between
instances, making copying TemplateArguments a trivial operation.
Currently getting the integral data out of a TemplateArgument requires creating
a new APSInt object. This is cheap when the value is small but can be expensive
if it's not. If this turns out to be an issue a more efficient accessor could
be added.
llvm-svn: 158150
In addition, I've made the pointer and reference typedef 'void' rather than T*
just so they can't get misused. I would've omitted them entirely but
std::distance likes them to be there even if it doesn't use them.
This rolls back r155808 and r155869.
Review by Doug Gregor incorporating feedback from Chandler Carruth.
llvm-svn: 158104
in-class initializer for one of its fields. Value-initialization of such
a type should use the in-class initializer!
The former was just a bug, the latter is a (reported) standard defect.
llvm-svn: 156274
filter_decl_iterator had a weird mismatch where both op* and op-> returned T*
making it difficult to generalize this filtering behavior into a reusable
library of any kind.
This change errs on the side of value, making op-> return T* and op* return
T&.
(reviewed by Richard Smith)
llvm-svn: 155808
track whether the referenced declaration comes from an enclosing
local context. I'm amenable to suggestions about the exact meaning
of this bit.
llvm-svn: 152491
- getSourceRange().getBegin() is about as awesome a pattern as .copy().size().
I already killed the hot paths so this doesn't seem to impact performance on my
tests-of-the-day, but it is a much more sensible (and shorter) pattern.
llvm-svn: 152419
data members for deleted or user-provided destructors.
Now it's computed in advance, serialize it, and in passing fix all the other
record DefinitionData flags whose serialization was missing.
llvm-svn: 151441
id-expression 'x' will compute the type based on the assumption that
'x' will be captured, even if it isn't captured, per C++11
[expr.prim.lambda]p18. There are two related refactors that go into
implementing this:
1) Split out the check that determines whether we should capture a
particular variable reference, along with the computation of the
type of the field, from the actual act of capturing the
variable.
2) Always compute the result of decltype() within Sema, rather than
AST, because the decltype() computation is now context-sensitive.
llvm-svn: 150347
to Redeclarable<NamespaceDecl>, so that we benefit from the improveed
redeclaration deserialization and merging logic provided by
Redeclarable<T>. Otherwise, no functionality change.
As a drive-by fix, collapse the "inline" bit into the low bit of the
original namespace/anonymous namespace, saving 8 bytes per
NamespaceDecl on x86_64.
llvm-svn: 147729
separately-allocated DefinitionData structure. Introduce various
functions that will help with the separation of declarations from
definitions (isThisDeclarationADefinition(), hasDefinition(),
getDefinition()).
llvm-svn: 147408
variable is initialized by a non-constant expression, and pass in the variable
being declared so that earlier-initialized fields' values can be used.
Rearrange VarDecl init evaluation to make this possible, and in so doing fix a
long-standing issue in our C++ constant expression handling, where we would
mishandle cases like:
extern const int a;
const int n = a;
const int a = 5;
int arr[n];
Here, n is not initialized by a constant expression, so can't be used in an ICE,
even though the initialization expression would be an ICE if it appeared later
in the TU. This requires computing whether the initializer is an ICE eagerly,
and saving that information in PCH files.
llvm-svn: 146856
declarations and definitions) as ObjCInterfaceDecls within the same
redeclaration chain. This new representation matches what we do for
C/C++ variables/functions/classes/templates/etc., and makes it
possible to answer the query "where are all of the declarations of
this class?"
llvm-svn: 146679
separately-allocated DefinitionData structure, which we manage the
same way as CXXRecordDecl::DefinitionData. This prepares the way for
making ObjCInterfaceDecls redeclarable, to more accurately model
forward declarations of Objective-C classes and eliminate the mutation
of ObjCInterfaceDecl that causes us serious trouble in the AST reader.
Note that ObjCInterfaceDecl's accessors are fairly robust against
being applied to forward declarations, because Clang (and Sema in
particular) doesn't perform RequireCompleteType/hasDefinition() checks
everywhere it has to. Each of these overly-robust cases is marked with
a FIXME, which we can tackle over time.
llvm-svn: 146644
to declaresSameEntity(), as a baby step toward tracking forward
declarations of Objective-C classes precisely. Part of
<rdar://problem/10583531>.
llvm-svn: 146618
it is going to be rewritten (and the chain will be serialized again), otherwise we may form a cycle in its
categories list when deserializing.
Also introduce ASTMutationListener::CompletedObjCForwardRef to notify that a forward reference
was completed; using Decl's isChangedSinceDeserialization/setChangedSinceDeserialization
is bug inducing and kinda gross, we should phase it out.
Fixes infinite loop in rdar://10418538.
llvm-svn: 144465
addDeclInternal(). This function suppresses any
calls to FindExternalVisibleDeclsByName() while
a Decl is added to a DeclContext. This behavior
is required for the ASTImporter, because in the
case of the LLDB client the ASTImporter would be
called recursively to import the visible decls,
which leads to assertions because the recursive
call is seeing partially-formed types.
I also modified the ASTImporter to use
addDeclInternal() in all places where it would
otherwise use addDecl(). This fix should not
affect the rest of Clang, passes Clang's
testsuite, and fixes several serious LLDB bugs.
llvm-svn: 142634
avoids loading data from an external source, since those lookups were
causing some "interesting" recursion in LLDB.
This code is not efficient. I plan to remedy this inefficiency in a
follow-up commit.
llvm-svn: 142023
- Remodel Expr::EvaluateAsInt to behave like the other EvaluateAs* functions,
and add Expr::EvaluateKnownConstInt to capture the current fold-or-assert
behaviour.
- Factor out evaluation of bitfield bit widths.
- Fix a few places which would evaluate an expression twice: once to determine
whether it is a constant expression, then again to get the value.
llvm-svn: 141561
-Add the location of the class name to all objc container decls, not just ObjCInterfaceDecl.
-Make objc decls consistent with the rest of the NamedDecls and have getLocation() point to the
class name, not the location of '@'.
llvm-svn: 141061
Instead of always storing all source locations for the selector identifiers
we check whether all the identifiers are in a "standard" position; "standard" position is
-Immediately before the arguments: -(id)first:(int)x second:(int)y;
-With a space between the arguments: -(id)first: (int)x second: (int)y;
-For nullary selectors, immediately before ';': -(void)release;
In such cases we infer the locations instead of storing them.
llvm-svn: 140989
, such as list of forward @class decls, in a DeclGroup
node. Deal with its consequence throught clang. This
is in preparation for more Sema work ahead. // rdar://8843851.
Feel free to reverse if it breaks something important
and I am unavailable.
llvm-svn: 138709
imported a forward declaration, but later the full definition of the
same entity becomes available. When this happens, import the definition.
llvm-svn: 136537
problem where Clang was setting the
hasExternalVisibleDecls() bit for all
DeclContexts it imported. This caused Clang
to make unnecessary calls to
findExternalVisibleDecls() when an external
AST source was installed.
In fact, Clang sometimes interpreted a failure
by one of these spurious calls to find a
Decl as meaning the Decl didn't exist, even
though findExternalLexicalDecls() did locate
that decl. This produced amusing errors of
the form:
-
error: no member named 'b' in 'A'; did you
mean 'b'?
-
Now, if hasExternalVisibleDecls() or
hasExternalLexicalDecls() should be set, the
external AST source must do so itself.
llvm-svn: 135824
in ImportDefinition when replacing a previously
forward-declared CXXRecordDecl with its full
definition. The forward-declared type's
DefinitionData had not been intialized for the
forward-declared type, so adding fields to the
Decl caused CXXRecordDecl::addedMember() to
crash when accessing the DefinitionData.
llvm-svn: 135530
for a template template parameter.
Uses to follow.
I've also made the uniquing of SubstTemplateTemplateParmPacks
use a ContextualFoldingSet as a minor space efficiency.
llvm-svn: 134137
Related result types apply Cocoa conventions to the type of message
sends and property accesses to Objective-C methods that are known to
always return objects whose type is the same as the type of the
receiving class (or a subclass thereof), such as +alloc and
-init. This tightens up static type safety for Objective-C, so that we
now diagnose mistakes like this:
t.m:4:10: warning: incompatible pointer types initializing 'NSSet *'
with an
expression of type 'NSArray *' [-Wincompatible-pointer-types]
NSSet *array = [[NSArray alloc] init];
^ ~~~~~~~~~~~~~~~~~~~~~~
/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:72:1:
note:
instance method 'init' is assumed to return an instance of its
receiver
type ('NSArray *')
- (id)init;
^
It also means that we get decent type inference when writing code in
Objective-C++0x:
auto array = [[NSMutableArray alloc] initWithObjects:@"one", @"two",nil];
// ^ now infers NSMutableArray* rather than id
llvm-svn: 132868
type that turns one type into another. This is used as the basis to
implement __underlying_type properly - with TypeSourceInfo and proper
behavior in the face of templates.
llvm-svn: 132017
Decl actually found via name lookup & overload resolution when that Decl
is different from the ValueDecl which is actually referenced by the
expression.
This can be used by AST consumers to correctly attribute references to
the spelling location of a using declaration, and otherwise gain insight
into the name resolution performed by Clang.
The public interface to DRE is kept as narrow as possible: we provide
a getFoundDecl() which always returns a NamedDecl, either the ValueDecl
referenced or the new, more precise NamedDecl if present. This way AST
clients can code against getFoundDecl without know when exactly the AST
has a split representation.
For an example of the data this provides consider:
% cat x.cc
namespace N1 {
struct S {};
void f(const S&);
}
void test(N1::S s) {
f(s);
using N1::f;
f(s);
}
% ./bin/clang -fsyntax-only -Xclang -ast-dump x.cc
[...]
void test(N1::S s) (CompoundStmt 0x5b02010 <x.cc:5:20, line:9:1>
(CallExpr 0x5b01df0 <line:6:3, col:6> 'void'
(ImplicitCastExpr 0x5b01dd8 <col:3> 'void (*)(const struct N1::S &)' <FunctionToPointerDecay>
(DeclRefExpr 0x5b01d80 <col:3> 'void (const struct N1::S &)' lvalue Function 0x5b01a20 'f' 'void (const struct N1::S &)'))
(ImplicitCastExpr 0x5b01e20 <col:5> 'const struct N1::S' lvalue <NoOp>
(DeclRefExpr 0x5b01d58 <col:5> 'N1::S':'struct N1::S' lvalue ParmVar 0x5b01b60 's' 'N1::S':'struct N1::S')))
(DeclStmt 0x5b01ee0 <line:7:3, col:14>
0x5b01e40 "UsingN1::;")
(CallExpr 0x5b01fc8 <line:8:3, col:6> 'void'
(ImplicitCastExpr 0x5b01fb0 <col:3> 'void (*)(const struct N1::S &)' <FunctionToPointerDecay>
(DeclRefExpr 0x5b01f80 <col:3> 'void (const struct N1::S &)' lvalue Function 0x5b01a20 'f' 'void (const struct N1::S &)' (UsingShadow 0x5b01ea0 'f')))
(ImplicitCastExpr 0x5b01ff8 <col:5> 'const struct N1::S' lvalue <NoOp>
(DeclRefExpr 0x5b01f58 <col:5> 'N1::S':'struct N1::S' lvalue ParmVar 0x5b01b60 's' 'N1::S':'struct N1::S'))))
Now we can tell that the second call is 'using' (no pun intended) the using
declaration, and *which* using declaration it sees. Without this, we can
mistake calls that go through using declarations for ADL calls, and have no way
to attribute names looked up with using declarations to the appropriate
UsingDecl.
llvm-svn: 130670
member function, i.e. something of the form 'x.f' where 'f' is a non-static
member function. Diagnose this in the general case. Some of the new diagnostics
are probably worse than the old ones, but we now get this right much more
universally, and there's certainly room for improvement in the diagnostics.
llvm-svn: 130239
The idea is that you can create a VarDecl with an unknown type, or a
FunctionDecl with an unknown return type, and it will still be valid to
access that object as long as you explicitly cast it at every use. I'm
still going back and forth about how I want to test this effectively, but
I wanted to go ahead and provide a skeletal implementation for the LLDB
folks' benefit and because it also improves some diagnostic goodness for
placeholder expressions.
llvm-svn: 129065
Change the interface to expose the new information and deal with the enormous fallout.
Introduce the new ExceptionSpecificationType value EST_DynamicNone to more easily deal with empty throw specifications.
Update the tests for noexcept and fix the various bugs uncovered, such as lack of tentative parsing support.
llvm-svn: 127537
Allow remapping a file by specifying another filename whose contents should be loaded if the original
file gets loaded. This allows to override files without having to create & load buffers in advance.
llvm-svn: 127052
Bruno Cardoso Lopes