Hi Hans, I'd really like to ship this change as part of Clang 3.6: there's an upcoming change to our behavior that will cause us to reject or differently interpret some code in C++11 and C++14 modes, and this patch adds a warning for the affected cases with a fix-it hint.
On Tue, Feb 10, 2015 at 6:41 PM, Richard Smith <[email protected]> wrote: > Author: rsmith > Date: Tue Feb 10 20:41:33 2015 > New Revision: 228792 > > URL: http://llvm.org/viewvc/llvm-project?rev=228792&view=rev > Log: > Add a warning for direct-list-initialization of a variable with a deduced > type > (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. > > Modified: > cfe/trunk/include/clang/Basic/DiagnosticGroups.td > cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td > cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td > cfe/trunk/lib/Parse/ParseExprCXX.cpp > cfe/trunk/lib/Sema/SemaDecl.cpp > cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp > cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp > cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm > cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp > > Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=228792&r1=228791&r2=228792&view=diff > > ============================================================================== > --- cfe/trunk/include/clang/Basic/DiagnosticGroups.td (original) > +++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td Tue Feb 10 20:41:33 > 2015 > @@ -750,3 +750,6 @@ def SerializedDiagnostics : DiagGroup<"s > // A warning group for warnings about code that clang accepts when > // compiling CUDA C/C++ but which is not compatible with the CUDA spec. > def CudaCompat : DiagGroup<"cuda-compat">; > + > +// A warning group for things that will change semantics in the future. > +def FutureCompat : DiagGroup<"future-compat">; > > Modified: cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td?rev=228792&r1=228791&r2=228792&view=diff > > ============================================================================== > --- cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td (original) > +++ cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td Tue Feb 10 > 20:41:33 2015 > @@ -804,6 +804,10 @@ def warn_cxx98_compat_lambda : Warning< > def err_lambda_missing_parens : Error< > "lambda requires '()' before %select{'mutable'|return type|" > "attribute specifier}0">; > +def warn_init_capture_direct_list_init : Warning< > + "direct list initialization of a lambda init-capture will change > meaning in " > + "a future version of Clang; insert an '=' to avoid a change in > behavior">, > + InGroup<FutureCompat>; > > // Availability attribute > def err_expected_version : Error< > > Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=228792&r1=228791&r2=228792&view=diff > > ============================================================================== > --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original) > +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Tue Feb 10 > 20:41:33 2015 > @@ -1645,6 +1645,10 @@ def err_auto_var_init_multiple_expressio > def err_auto_var_init_paren_braces : Error< > "cannot deduce type for variable %0 with type %1 from " > "parenthesized initializer list">; > +def warn_auto_var_direct_list_init : Warning< > + "direct list initialization of a variable with a deduced type will > change " > + "meaning in a future version of Clang; insert an '=' to avoid a change > in " > + "behavior">, InGroup<FutureCompat>; > def err_auto_new_ctor_multiple_expressions : Error< > "new expression for type %0 contains multiple constructor arguments">; > def err_auto_missing_trailing_return : Error< > > Modified: cfe/trunk/lib/Parse/ParseExprCXX.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseExprCXX.cpp?rev=228792&r1=228791&r2=228792&view=diff > > ============================================================================== > --- cfe/trunk/lib/Parse/ParseExprCXX.cpp (original) > +++ cfe/trunk/lib/Parse/ParseExprCXX.cpp Tue Feb 10 20:41:33 2015 > @@ -894,11 +894,16 @@ Optional<unsigned> Parser::ParseLambdaIn > // to save the necessary state, and restore it later. > EnterExpressionEvaluationContext EC(Actions, > Sema::PotentiallyEvaluated); > - TryConsumeToken(tok::equal); > + bool HadEquals = TryConsumeToken(tok::equal); > > - if (!SkippedInits) > + if (!SkippedInits) { > + // Warn on constructs that will change meaning when we > implement N3922 > + if (!HadEquals && Tok.is(tok::l_brace)) { > + Diag(Tok, diag::warn_init_capture_direct_list_init) > + << FixItHint::CreateInsertion(Tok.getLocation(), "="); > + } > Init = ParseInitializer(); > - else if (Tok.is(tok::l_brace)) { > + } else if (Tok.is(tok::l_brace)) { > BalancedDelimiterTracker Braces(*this, tok::l_brace); > Braces.consumeOpen(); > Braces.skipToEnd(); > > Modified: cfe/trunk/lib/Sema/SemaDecl.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=228792&r1=228791&r2=228792&view=diff > > ============================================================================== > --- cfe/trunk/lib/Sema/SemaDecl.cpp (original) > +++ cfe/trunk/lib/Sema/SemaDecl.cpp Tue Feb 10 20:41:33 2015 > @@ -8716,6 +8716,14 @@ void Sema::AddInitializerToDecl(Decl *Re > CheckVariableDeclarationType(VDecl); > if (VDecl->isInvalidDecl()) > return; > + > + // If all looks well, warn if this is a case that will change meaning > when > + // we implement N3922. > + if (DirectInit && !CXXDirectInit && isa<InitListExpr>(Init)) { > + Diag(Init->getLocStart(), > + diag::warn_auto_var_direct_list_init) > + << FixItHint::CreateInsertion(Init->getLocStart(), "="); > + } > } > > // dllimport cannot be used on variable definitions. > > Modified: cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp?rev=228792&r1=228791&r2=228792&view=diff > > ============================================================================== > --- cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp > (original) > +++ cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp Tue Feb > 10 20:41:33 2015 > @@ -48,7 +48,7 @@ auto bad_init_2 = [a(1, 2)] {}; // expec > auto bad_init_3 = [&a(void_fn())] {}; // expected-error {{cannot form a > reference to 'void'}} > auto bad_init_4 = [a(void_fn())] {}; // expected-error {{has incomplete > type 'void'}} > auto bad_init_5 = [a(overload_fn)] {}; // expected-error {{cannot deduce > type for lambda capture 'a' from initializer of type '<overloaded function}} > -auto bad_init_6 = [a{overload_fn}] {}; // expected-error {{cannot deduce > type for lambda capture 'a' from initializer list}} > +auto bad_init_6 = [a{overload_fn}] {}; // expected-error {{cannot deduce > type for lambda capture 'a' from initializer list}} expected-warning {{will > change meaning in a future version of Clang}} > > template<typename...T> void pack_1(T...t) { (void)[a(t...)] {}; } // > expected-error {{initializer missing for lambda capture 'a'}} > template void pack_1<>(); // expected-note {{instantiation of}} > @@ -61,7 +61,7 @@ auto a = [a(4), b = 5, &c = static_cast< > using T = decltype(c); > using T = const int &; > }; > -auto b = [a{0}] {}; // expected-error {{include <initializer_list>}} > +auto b = [a{0}] {}; // expected-error {{include <initializer_list>}} > expected-warning {{will change meaning in a future version of Clang}} > > struct S { S(); S(S&&); }; > template<typename T> struct remove_reference { typedef T type; }; > > Modified: cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp?rev=228792&r1=228791&r2=228792&view=diff > > ============================================================================== > --- cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp (original) > +++ cfe/trunk/test/Parser/cxx0x-lambda-expressions.cpp Tue Feb 10 20:41:33 > 2015 > @@ -61,7 +61,7 @@ class C { > int z; > void init_capture() { > [n(0)] () mutable -> int { return ++n; }; // > expected-warning{{extension}} > - [n{0}] { return; }; // expected-error {{<initializer_list>}} > expected-warning{{extension}} > + [n{0}] { return; }; // expected-error {{<initializer_list>}} > expected-warning{{extension}} expected-warning{{will change meaning in a > future version}} > [n = 0] { return ++n; }; // expected-error {{captured by copy in a > non-mutable}} expected-warning{{extension}} > [n = {0}] { return; }; // expected-error {{<initializer_list>}} > expected-warning{{extension}} > [a([&b = z]{})](){}; // expected-warning 2{{extension}} > > Modified: cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm?rev=228792&r1=228791&r2=228792&view=diff > > ============================================================================== > --- cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm (original) > +++ cfe/trunk/test/Parser/objcxx0x-lambda-expressions.mm Tue Feb 10 > 20:41:33 2015 > @@ -21,7 +21,7 @@ class C { > > [foo(bar)] () {}; > [foo = bar] () {}; > - [foo{bar}] () {}; // expected-error {{<initializer_list>}} > + [foo{bar}] () {}; // expected-error {{<initializer_list>}} > expected-warning {{will change meaning}} > [foo = {bar}] () {}; // expected-error {{<initializer_list>}} > > [foo(bar) baz] () {}; // expected-error {{called object type 'int' is > not a function}} > > Modified: cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp?rev=228792&r1=228791&r2=228792&view=diff > > ============================================================================== > --- cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp > (original) > +++ cfe/trunk/test/SemaCXX/cxx0x-initializer-stdinitializerlist.cpp Tue > Feb 10 20:41:33 2015 > @@ -117,6 +117,7 @@ void argument_deduction() { > > void auto_deduction() { > auto l = {1, 2, 3, 4}; > + auto l2 {1, 2, 3, 4}; // expected-warning {{will change meaning in a > future version of Clang}} > static_assert(same_type<decltype(l), > std::initializer_list<int>>::value, ""); > auto bl = {1, 2.0}; // expected-error {{cannot deduce}} > > > > _______________________________________________ > cfe-commits mailing list > [email protected] > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits >
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