[cfe-commits] r147599 - in /cfe/trunk: include/clang/Basic/DiagnosticGroups.td include/clang/Basic/DiagnosticParseKinds.td include/clang/Sema/DeclSpec.h lib/Parse/ParseDecl.cpp test/CXX/basic/basic.link/p9.cpp test/CXX/dcl.dcl/basic.namespace/nam

[David Blaikie]

That does seem a little overly restrictive to me. It's not an uncommon
newbie mistake to add the empty parens for an object construction even
on a trivial user defined type. The user then gets a fairly weird
message in their use case about how they can't pass a foo(*)() as a foo
(or worse, no overload is available, along with a big list of overload
candidates). Providing a more likely warning before all this confusing
noise seems really valuable.

(at some point it'd be great to really improve the original most vexing
parse warning too so it's produced on the really vexing cases in
non-function scope (currently the warning doesn't fire at all there)
and provide some nice fixit notes to fix the usual case ("foo f(bar())"
-> "foo f((bar()))")))
From: Richard Smith
Sent: 1/5/2012 3:40 PM
To: Argyrios Kyrtzidis
Cc: cfe-commits at cs.uiuc.edu
Subject: Re: [cfe-commits] r147599 - in /cfe/trunk:
include/clang/Basic/DiagnosticGroups.td
include/clang/Basic/DiagnosticParseKinds.td
include/clang/Sema/DeclSpec.h lib/Parse/ParseDecl.cpp
test/CXX/basic/basic.link/p9.cpp
test/CXX/dcl.dcl/basic.namespace/namespace.udecl/p11.cpp
test/Misc/warning-flags.c test/SemaCXX/conditional-expr.cpp
test/SemaCXX/decl-expr-ambiguity.cpp
test/SemaTemplate/class-template-ctor-initializer.cpp
On Thu, January 5, 2012 04:50, Argyrios Kyrtzidis wrote:
> On Jan 4, 2012, at 8:12 PM, Richard Smith wrote:
>> Author: rsmith
>> Date: Wed Jan  4 22:12:21 2012
>> New Revision: 147599
>>
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=147599&view=rev
>> Log:
>> PR10828: Produce a warning when a no-arguments function is declared in block
>>  scope, when no other indication is provided that the user intended to
>> declare a function rather than a variable.
>>
>> Remove some false positives from the existing 'parentheses disambiguated as
>> a function' warning by suppressing it when the declaration is marked as
>> 'typedef'
>> or 'extern'.
>>
>> Add a new warning group -Wvexing-parse containing both of these warnings.
>>
>>
>> The new warning is enabled by default; despite a number of false positives
>> (and
>> one bug) in clang's test-suite, I have only found genuine bugs with it when
>> running it over a significant quantity of real C++ code.
[...]
> 2) The new warning belongs in the sema, not the parser, because it requires
> semantic checks; consider the following case:
>
> void f() { typedef void VOID; VOID gg();  // false positive here.
> }

r147642. I've also restricted it to class types; I've not seen any instances
of this for non-class types, and they're the types for which we can silently
miss important RAII actions. I'd be happy to change this behavior if anyone
has experience or evidence which points in a different direction.

- Richard

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