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
r235046 turned "extern __declspec(selectany) int a;" from a declaration into
a definition to fix PR23242 (required for compatibility with mc.exe output).
However, this broke parsing Windows headers: A d3d11 headers contain something
like
struct SomeStruct {};
extern const __declspec(selectany) SomeStruct some_struct;
This is now a definition, and const objects either need an explicit default
ctor or an initializer so this errors out with
d3d11.h(1065,48) :
error: default initialization of an object of const type
'const CD3D11_DEFAULT' without a user-provided default constructor
(cl.exe just doesn't implement this rule, independent of selectany.)
To work around this, weaken this error into a warning for selectany decls
in microsoft mode, and recover with zero-initialization.
Doing this is a bit hairy since it adds a fixit on an error emitted
by InitializationSequence – this means it needs to build a correct AST, which
in turn means InitializationSequence::Failed() cannot return true when this
fixit is applied. As a workaround, the patch adds a fixit member to
InitializationSequence, and InitializationSequence::Perform() prints the
diagnostic if the fixit member is set right after its call to Diagnose.
That function is usually called when InitializationSequences are used –
InitListChecker::PerformEmptyInit() doesn't call it, but the InitListChecker
case never performs default-initialization, so this is technically OK.
This is the alternative, original fix for PR20208 that got reviewed in the
thread "[patch] Improve diagnostic on default-initializing const variables
(PR20208)". This change basically reverts r213725, adds the original fix for
PR20208, and makes the error a warning in Microsoft mode.
llvm-svn: 235166
This tweaks the diagnostic wording slighly, and adds a fixit on a note.
An alternative would be to add the fixit directly on the diagnostic, see
the review thread linked to from the bug for a few notes on that approach.
llvm-svn: 213725
should use a constructor to default-initialize a
variable. InitializationSequence knows the rules for default
initialization, better. Fixes <rdar://problem/8501008>.
llvm-svn: 131796
therefore not creating ElaboratedTypes, which are still pretty-printed
with the written tag).
Most of these testcase changes were done by script, so don't feel too
sorry for my fingers.
llvm-svn: 98149
uninitialized. This seems not to be the case in C++0x, where we still
call the (trivial) default constructor for a POD class
(!). Previously, we had implemented only the C++0x rules; now we
implement both. Fixes PR6536.
llvm-svn: 97928
Sema::ActOnUninitializedDecl over to InitializationSequence (with
default initialization), eliminating redundancy. More importantly, we
now check that a const definition in C++ has an initilizer, which was
an #if 0'd code for many, many months. A few other tweaks were needed
to get everything working again:
- Fix all of the places in the testsuite where we defined const
objects without initializers (now that we diagnose this issue)
- Teach instantiation of static data members to find the previous
declaration, so that we build proper redeclaration
chains. Previously, we had the redeclaration chain but built it
too late to be useful, because...
- Teach instantiation of static data member definitions not to try
to check an initializer if a previous declaration already had an
initializer. This makes sure that we don't complain about static
const data members with in-class initializers and out-of-line
definitions.
- Move all of the incomplete-type checking logic out of
Sema::FinalizeDeclaratorGroup; it makes more sense in
ActOnUnitializedDecl.
There may still be a few places where we can improve these
diagnostics. I'll address that as a separate commit.
llvm-svn: 95657
(necessarily simultaneous) changes:
- CXXBaseOrMemberInitializer now contains only a single initializer
rather than a set of initialiation arguments + a constructor. The
single initializer covers all aspects of initialization, including
constructor calls as necessary but also cleanup of temporaries
created by the initializer (which we never handled
before!).
- Rework + simplify code generation for CXXBaseOrMemberInitializers,
since we can now just emit the initializer as an initializer.
- Switched base and member initialization over to the new
initialization code (InitializationSequence), so that it
- Improved diagnostics for the new initialization code when
initializing bases and members, to match the diagnostics produced
by the previous (special-purpose) code.
- Simplify the representation of type-checked constructor initializers in
templates; instead of keeping the fully-type-checked AST, which is
rather hard to undo at template instantiation time, throw away the
type-checked AST and store the raw expressions in the AST. This
simplifies instantiation, but loses a little but of information in
the AST.
- When type-checking implicit base or member initializers within a
dependent context, don't add the generated initializers into the
AST, because they'll look like they were explicit.
- Record in CXXConstructExpr when the constructor call is to
initialize a base class, so that CodeGen does not have to infer it
from context. This ensures that we call the right kind of
constructor.
There are also a few "opportunity" fixes here that were needed to not
regress, for example:
- Diagnose default-initialization of a const-qualified class that
does not have a user-declared default constructor. We had this
diagnostic specifically for bases and members, but missed it for
variables. That's fixed now.
- When defining the implicit constructors, destructor, and
copy-assignment operator, set the CurContext to that constructor
when we're defining the body.
llvm-svn: 94952
Nico Weber