r194869 - PR8455: Handle an attribute between a goto label and a variable declaration per
Richard Smith
richard at metafoo.co.uk
Fri Nov 15 15:42:37 PST 2013
On Fri, Nov 15, 2013 at 3:33 PM, Alp Toker <alp at nuanti.com> wrote:
> Hello Richard,
>
> For the record I had a patch up for review to fix this back from 2010, not
> sure if it ever reached the list:
>
> http://llvm.org/bugs/show_bug.cgi?id=8455
>
> Just to compare notes, my approach was to use a TentativeParsingAction to
> handle some of the corner cases.
>
Aaron's original patch went in that direction, but got reworked to avoid
the cost of a tentative parse.
> Alp.
>
>
>
>
> On 15/11/2013 22:45, Richard Smith wrote:
>
>> Author: rsmith
>> Date: Fri Nov 15 16:45:29 2013
>> New Revision: 194869
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=194869&view=rev
>> Log:
>> PR8455: Handle an attribute between a goto label and a variable
>> declaration per
>> the GNU documentation: the attribute only appertains to the label if it is
>> followed by a semicolon. Based on a patch by Aaron Ballman!
>>
>> Modified:
>> cfe/trunk/lib/Parse/ParseStmt.cpp
>> cfe/trunk/test/Misc/ast-dump-attr.cpp
>> cfe/trunk/test/Sema/warn-unused-label.c
>> cfe/trunk/test/SemaCXX/warn-unused-variables.cpp
>>
>> Modified: cfe/trunk/lib/Parse/ParseStmt.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/
>> ParseStmt.cpp?rev=194869&r1=194868&r2=194869&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/lib/Parse/ParseStmt.cpp (original)
>> +++ cfe/trunk/lib/Parse/ParseStmt.cpp Fri Nov 15 16:45:29 2013
>> @@ -516,11 +516,40 @@ StmtResult Parser::ParseLabeledStatement
>> // identifier ':' statement
>> SourceLocation ColonLoc = ConsumeToken();
>> - // Read label attributes, if present. attrs will contain both C++11
>> and GNU
>> - // attributes (if present) after this point.
>> - MaybeParseGNUAttributes(attrs);
>> + // Read label attributes, if present.
>> + StmtResult SubStmt;
>> + if (Tok.is(tok::kw___attribute)) {
>> + ParsedAttributesWithRange TempAttrs(AttrFactory);
>> + ParseGNUAttributes(TempAttrs);
>> +
>> + // In C++, GNU attributes only apply to the label if they are
>> followed by a
>> + // semicolon, to disambiguate label attributes from attributes on a
>> labeled
>> + // declaration.
>> + //
>> + // This doesn't quite match what GCC does; if the attribute list is
>> empty
>> + // and followed by a semicolon, GCC will reject (it appears to parse
>> the
>> + // attributes as part of a statement in that case). That looks like
>> a bug.
>> + if (!getLangOpts().CPlusPlus || Tok.is(tok::semi))
>> + attrs.takeAllFrom(TempAttrs);
>> + else if (isDeclarationStatement()) {
>> + StmtVector Stmts;
>> + // FIXME: We should do this whether or not we have a declaration
>> + // statement, but that doesn't work correctly (because
>> ProhibitAttributes
>> + // can't handle GNU attributes), so only call it in the one case
>> where
>> + // GNU attributes are allowed.
>> + SubStmt = ParseStatementOrDeclarationAfterAttributes(
>> + Stmts, /*OnlyStmts*/ true, 0, TempAttrs);
>> + if (!TempAttrs.empty() && !SubStmt.isInvalid())
>> + SubStmt = Actions.ProcessStmtAttributes(
>> + SubStmt.get(), TempAttrs.getList(), TempAttrs.Range);
>> + } else {
>> + Diag(Tok, diag::err_expected_semi_after) << "__attribute__";
>> + }
>> + }
>> - StmtResult SubStmt(ParseStatement());
>> + // If we've not parsed a statement yet, parse one now.
>> + if (!SubStmt.isInvalid() && !SubStmt.isUsable())
>> + SubStmt = ParseStatement();
>> // Broken substmt shouldn't prevent the label from being added to
>> the AST.
>> if (SubStmt.isInvalid())
>> @@ -557,7 +586,7 @@ StmtResult Parser::ParseCaseStatement(bo
>> // out of stack space in our recursive descent parser. As a special
>> case,
>> // flatten this recursion into an iterative loop. This is complex
>> and gross,
>> // but all the grossness is constrained to ParseCaseStatement (and
>> some
>> - // wierdness in the actions), so this is just local grossness :).
>> + // weirdness in the actions), so this is just local grossness :).
>> // TopLevelCase - This is the highest level we have parsed. 'case
>> 1' in the
>> // example above.
>>
>> Modified: cfe/trunk/test/Misc/ast-dump-attr.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Misc/
>> ast-dump-attr.cpp?rev=194869&r1=194868&r2=194869&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/test/Misc/ast-dump-attr.cpp (original)
>> +++ cfe/trunk/test/Misc/ast-dump-attr.cpp Fri Nov 15 16:45:29 2013
>> @@ -95,3 +95,19 @@ void *TestVariadicUnsigned1(int) __attri
>> void *TestVariadicUnsigned2(int, int) __attribute__((alloc_size(1,2)));
>> // CHECK: FunctionDecl{{.*}}TestVariadicUnsigned2
>> // CHECK: AllocSizeAttr{{.*}} 0 1
>> +
>> +void TestLabel() {
>> +L: __attribute__((unused)) int i;
>> +// CHECK: LabelStmt{{.*}}'L'
>> +// CHECK: VarDecl{{.*}}i 'int'
>> +// CHECK-NEXT: UnusedAttr{{.*}}
>> +
>> +M: __attribute(()) int j;
>> +// CHECK: LabelStmt {{.*}} 'M'
>> +// CHECK-NEXT: DeclStmt
>> +// CHECK-NEXT: VarDecl {{.*}} j 'int'
>> +
>> +N: __attribute(()) ;
>> +// CHECK: LabelStmt {{.*}} 'N'
>> +// CHECK-NEXT: NullStmt
>> +}
>>
>> Modified: cfe/trunk/test/Sema/warn-unused-label.c
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/
>> warn-unused-label.c?rev=194869&r1=194868&r2=194869&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/test/Sema/warn-unused-label.c (original)
>> +++ cfe/trunk/test/Sema/warn-unused-label.c Fri Nov 15 16:45:29 2013
>> @@ -9,3 +9,7 @@ void f() {
>> goto d;
>> return;
>> }
>> +
>> +void PR8455() {
>> + L: __attribute__((unused)) return; // ok, no semicolon required
>> +}
>>
>> Modified: cfe/trunk/test/SemaCXX/warn-unused-variables.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/
>> SemaCXX/warn-unused-variables.cpp?rev=194869&r1=194868&r2=
>> 194869&view=diff
>> ============================================================
>> ==================
>> --- cfe/trunk/test/SemaCXX/warn-unused-variables.cpp (original)
>> +++ cfe/trunk/test/SemaCXX/warn-unused-variables.cpp Fri Nov 15 16:45:29
>> 2013
>> @@ -1,4 +1,4 @@
>> -// RUN: %clang_cc1 -fsyntax-only -Wunused-variable -verify %s
>> +// RUN: %clang_cc1 -fsyntax-only -Wunused-variable -Wunused-label
>> -verify %s
>> template<typename T> void f() {
>> T t;
>> t = 17;
>> @@ -128,3 +128,26 @@ namespace ctor_with_cleanups {
>> }
>> #include "Inputs/warn-unused-variables.h"
>> +
>> +namespace PR8455 {
>> + void f() {
>> + A: // expected-warning {{unused label 'A'}}
>> + __attribute__((unused)) int i; // attribute applies to variable
>> + B: // attribute applies to label
>> + __attribute__((unused)); int j; // expected-warning {{unused
>> variable 'j'}}
>> + }
>> +
>> + void g() {
>> + C: // unused label 'C' will not appear here because an error occurs
>> + __attribute__((unused))
>> + #pragma weak unused_local_static // expected-error {{expected ';'
>> after __attribute__}}
>> + ;
>> + }
>> +
>> + void h() {
>> + D: // expected-warning {{unused label 'D'}}
>> + #pragma weak unused_local_static
>> + __attribute__((unused)) // expected-warning {{declaration does
>> not declare anything}}
>> + ;
>> + }
>> +}
>>
>>
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>
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