[PATCH] Fix to PR15845 - Clang accepts invalid code
Richard Smith
richard at metafoo.co.uk
Tue Apr 30 02:08:40 PDT 2013
On 29 Apr 2013 20:01, "Aaron Ballman" <aaron at aaronballman.com> wrote:
>
> Correct; since we're going to be modifying the way this extension
> works, it would be great if we could make it more compatible for
> -fms-compatibility. In this case, MSVC handles void func(xxx) {} when
> /TC is passed in, so it would be good for clang to do so as well
> (along with the other cases that Richard pointed out).
That is unrelated to implicit int in c++, which the current patch
addresses, and is in fact unrelated to implicit int at all - Serge
confirmed that this is treated as an (ignored) identifier- list, not as a
parameter with implicit int.
Unless you have evidence that we need this extension, I don't see any
reason to implement it.
> ~Aaron
>
> On Mon, Apr 29, 2013 at 1:56 PM, Serge Pavlov <sepavloff at gmail.com> wrote:
> > Clang now allows implicit int in C mode (-x c) in some cases:
> >
> > abc = 1;
> > static foo() { return 1; }
> >
> > But in function declaration it is now forbidden unlike to GCC and MSVC:
> >
> > void func(xxx);
> >
> > --Serge
> >
> >
> >
> >
> > 2013/4/30 Aaron Ballman <aaron at aaronballman.com>
> >>
> >> To be clear, MSVC does accept that code so long as you pass in the /TC
> >> flag. So, for instance, the test cases with a .c or .m extension
> >> should allow the implicit int (by default .c files are compiled with
> >> /TC in MSVC), but the .cpp/.mm files should disallow it (unless we
> >> force compilation as C with -x c, which would be the clang version of
> >> /TC).
> >>
> >> ~Aaron
> >>
> >> On Mon, Apr 29, 2013 at 1:31 PM, Serge Pavlov <sepavloff at gmail.com>
wrote:
> >> > Hi Richard,
> >> >
> >> >
> >> > 2013/4/29 Richard Smith <richard at metafoo.co.uk>
> >> > [...]
> >> >>
> >> >> The problem is that clang in C++ mode accepts the code:
> >> >>>
> >> >>> int foo(xxx);
> >> >>> Clang intentionally accepts this code due to a check in
> >> >>> Parser::ParseImplicitInt, which appeared in r156854.
> >> >>> The comment in the inserted code states that MS supports implicit
int
> >> >>> in
> >> >>> C++ mode, however it looks like none of VS2005, VS2008, VS2010 or
> >> >>> VS2012
> >> >>> does it. So removing the check for MS extension solves the problem.
> >> >>
> >> >>
> >> >> If it is indeed the case that MSVC does not allow implicit int in
C++,
> >> >> then we should absolutely remove that "extension". However, someone
> >> >> presumably added it for a reason, so I'd like to be sure that we've
> >> >> checked
> >> >> this thoroughly before proceeding. Does MSVC allow implicit int in
any
> >> >> other
> >> >> contexts? For instance...
> >> >
> >> >
> >> > MSVC doesn't allow implicit int in any context if in C++ mode,
details
> >> > are
> >> > in bugzilla.
> >> >
> >> >>
> >> >>
> >> >> const n = 0; // ok?
> >> >> static f() { // ok?
> >> >> extern m; // ok?
> >> >> return m;
> >> >> }
> >> >
> >> >
> >> > None of these cases are accepted by MSVC.
> >> >
> >> >>
> >> >> If MSVC does allow these, then the fix is different: the
> >> >> decl-specifier-seq (or, in C, the declaration-specifiers) for a
> >> >> parameter
> >> >> cannot be empty, so 'int foo(xxx);' would not have implicit int
> >> >> applied,
> >> >> whereas 'int foo(const xxx);' would, and we should make the parser
> >> >> handle
> >> >> that correctly.
> >> >>
> >> >>>
> >> >>> Another problem - the same code compiled in C mode produces an
error,
> >> >>> while both GCC and MSC accept it. To fix it the message
> >> >>> err_ident_list_in_fn_declaration was converted into warning.
> >> >>
> >> >>
> >> >> Have you checked whether they treat it as an implicit int, or
whether
> >> >> they
> >> >> treat it as an (ignored, presumably) identifier list?
> >> >
> >> >
> >> > They are ignored. For instance, both MSVC and GCC successfully
compile
> >> > the
> >> > following code:
> >> >
> >> > void abc(xxx);
> >> > void abc(int x, char*y) {}
> >> >
> >> >>
> >> >> Also, do you actually have code which relies upon this extension? If
> >> >> not,
> >> >> let's not add it gratuitously.
> >> >
> >> >
> >> > I know nothing about such, the intent was to make behavior more
> >> > compatible.
> >> > Probably it doesn't worth implementation.
> >> >
> >> >> Please split this into its two constituent changes (removing
implicit
> >> >> int
> >> >> in microsoft mode, and accepting an identifier-list in a
non-defining
> >> >> function declaration). They're basically unrelated, and make more
sense
> >> >> to
> >> >> review separately.
> >> >
> >> >
> >> > OK. This patch only removes implicit int in MS-compatibility mode for
> >> > C++.
> >> > Fix to accepting an identifier-list in a non-defining function
> >> > declaration
> >> > is dropped.
> >> >
> >> >>>
> >> >>> Files:
> >> >>> include/clang/Basic/DiagnosticSemaKinds.td
> >> >>> lib/Parse/ParseDecl.cpp
> >> >>> lib/Sema/SemaType.cpp
> >> >>> test/Sema/MicrosoftCompatibility.cpp
> >> >>> test/Sema/alloc_size.c
> >> >>> test/Sema/function.c
> >> >>> test/Sema/invalid-decl.c
> >> >>>
> >> >>>
> >> >>>
> >> >>>
-----------------------------------------------------------------------------------------------------
> >> >>> diff --git a/include/clang/Basic/DiagnosticSemaKinds.td
> >> >>> b/include/clang/Basic/DiagnosticSemaKinds.td
> >> >>> index 1461716..166dbab 100644
> >> >>> --- a/include/clang/Basic/DiagnosticSemaKinds.td
> >> >>> +++ b/include/clang/Basic/DiagnosticSemaKinds.td
> >> >>> @@ -2314,8 +2314,9 @@ def err_void_only_param : Error<
> >> >>> "'void' must be the first and only parameter if specified">;
> >> >>> def err_void_param_qualified : Error<
> >> >>> "'void' as parameter must not have type qualifiers">;
> >> >>> -def err_ident_list_in_fn_declaration : Error<
> >> >>> - "a parameter list without types is only allowed in a function
> >> >>> definition">;
> >> >>> +def warn_ident_list_in_fn_declaration : Warning<
> >> >>> + "a parameter list without types is only allowed in a function
> >> >>> definition">,
> >> >>> + InGroup<C99Compat>;
> >> >>
> >> >>
> >> >> This should be an ExtWarn, not a Warning, since this is a required
> >> >> diagnostic per the various C language standards. Also, C99Compat
seems
> >> >> wrong.
> >> >
> >> >
> >> > Thank you for the explanation.
> >> >
> >> >>
> >> >>>
> >> >>> def ext_param_not_declared : Extension<
> >> >>> "parameter %0 was not declared, defaulting to type 'int'">;
> >> >>> def err_param_typedef_of_void : Error<
> >> >>> diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
> >> >>> index d786ce2..2f0c1a3 100644
> >> >>> --- a/lib/Parse/ParseDecl.cpp
> >> >>> +++ b/lib/Parse/ParseDecl.cpp
> >> >>> @@ -2038,10 +2038,9 @@ bool Parser::ParseImplicitInt(DeclSpec &DS,
> >> >>> CXXScopeSpec *SS,
> >> >>> // error, do lookahead to try to do better recovery. This never
> >> >>> applies
> >> >>> // within a type specifier. Outside of C++, we allow this even
if
> >> >>> the
> >> >>> // language doesn't "officially" support implicit int -- we
support
> >> >>> - // implicit int as an extension in C99 and C11. Allegedly, MS
also
> >> >>> - // supports implicit int in C++ mode.
> >> >>> + // implicit int as an extension in C99 and C11.
> >> >>> if (DSC != DSC_type_specifier && DSC != DSC_trailing &&
> >> >>> - (!getLangOpts().CPlusPlus || getLangOpts().MicrosoftExt) &&
> >> >>> + !getLangOpts().CPlusPlus &&
> >> >>
> >> >>
> >> >> There is a matching check in lib/Sema/DeclSpec.cpp, and possibly
> >> >> elsewhere. If we're not enabling implicit int in -fms-extensions
mode,
> >> >> we
> >> >> need to do that consistently throughout the compiler.
> >> >
> >> >
> >> > Indeed, SemaType.cpp also contains similar check.
> >> >
> >> >>>
> >> >>> isValidAfterIdentifierInDeclarator(NextToken())) {
> >> >>> // If this token is valid for implicit int, e.g. "static x =
4",
> >> >>> then
> >> >>> // we just avoid eating the identifier, so it will be parsed
as
> >> >>> the
> >> >>> diff --git a/lib/Sema/SemaType.cpp b/lib/Sema/SemaType.cpp
> >> >>> index 8bf5143..243b772 100644
> >> >>> --- a/lib/Sema/SemaType.cpp
> >> >>> +++ b/lib/Sema/SemaType.cpp
> >> >>> @@ -2742,7 +2742,7 @@ static TypeSourceInfo
> >> >>> *GetFullTypeForDeclarator(TypeProcessingState &state,
> >> >>> if (FTI.NumArgs && FTI.ArgInfo[0].Param == 0) {
> >> >>> // C99 6.7.5.3p3: Reject int(x,y,z) when it's not a
> >> >>> function
> >> >>> // definition.
> >> >>> - S.Diag(FTI.ArgInfo[0].IdentLoc,
> >> >>> diag::err_ident_list_in_fn_declaration);
> >> >>> + S.Diag(FTI.ArgInfo[0].IdentLoc,
> >> >>> diag::warn_ident_list_in_fn_declaration);
> >> >>> D.setInvalidType(true);
> >> >>
> >> >>
> >> >> If you're not issuing an error, you must build a correct AST -- you
> >> >> can't
> >> >> set things invalid.
> >> >>
> >> >
> >> > My fault...
> >> > [...]
> >> >
> >> >
> >> > Updated patch:
> >> >
> >> > Files:
> >> > lib/Parse/ParseDecl.cpp
> >> > lib/Sema/DeclSpec.cpp
> >> > lib/Sema/SemaType.cpp
> >> > test/Rewriter/rewrite-byref-in-nested-blocks.mm
> >> > test/Sema/MicrosoftCompatibility.cpp
> >> >
> >> >
> >> > diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
> >> > index d786ce2..2f0c1a3 100644
> >> > --- a/lib/Parse/ParseDecl.cpp
> >> > +++ b/lib/Parse/ParseDecl.cpp
> >> > @@ -2038,10 +2038,9 @@ bool Parser::ParseImplicitInt(DeclSpec &DS,
> >> > CXXScopeSpec *SS,
> >> > // error, do lookahead to try to do better recovery. This never
> >> > applies
> >> > // within a type specifier. Outside of C++, we allow this even if
the
> >> > // language doesn't "officially" support implicit int -- we
support
> >> > - // implicit int as an extension in C99 and C11. Allegedly, MS also
> >> > - // supports implicit int in C++ mode.
> >> > + // implicit int as an extension in C99 and C11.
> >> > if (DSC != DSC_type_specifier && DSC != DSC_trailing &&
> >> > - (!getLangOpts().CPlusPlus || getLangOpts().MicrosoftExt) &&
> >> > + !getLangOpts().CPlusPlus &&
> >> > isValidAfterIdentifierInDeclarator(NextToken())) {
> >> > // If this token is valid for implicit int, e.g. "static x = 4",
> >> > then
> >> > // we just avoid eating the identifier, so it will be parsed as
the
> >> > diff --git a/lib/Sema/DeclSpec.cpp b/lib/Sema/DeclSpec.cpp
> >> > index 124f50c..3b3ab2c 100644
> >> > --- a/lib/Sema/DeclSpec.cpp
> >> > +++ b/lib/Sema/DeclSpec.cpp
> >> > @@ -1003,8 +1003,7 @@ void DeclSpec::Finish(DiagnosticsEngine &D,
> >> > Preprocessor &PP) {
> >> > // the type specifier is not optional, but we got 'auto' as a
storage
> >> > // class specifier, then assume this is an attempt to use C++0x's
> >> > 'auto'
> >> > // type specifier.
> >> > - // FIXME: Does Microsoft really support implicit int in C++?
> >> > - if (PP.getLangOpts().CPlusPlus && !PP.getLangOpts().MicrosoftExt
&&
> >> > + if (PP.getLangOpts().CPlusPlus &&
> >> > TypeSpecType == TST_unspecified && StorageClassSpec ==
SCS_auto)
> >> > {
> >> > TypeSpecType = TST_auto;
> >> > StorageClassSpec = SCS_unspecified;
> >> > diff --git a/lib/Sema/SemaType.cpp b/lib/Sema/SemaType.cpp
> >> > index 8bf5143..2038f12 100644
> >> > --- a/lib/Sema/SemaType.cpp
> >> > +++ b/lib/Sema/SemaType.cpp
> >> > @@ -793,9 +793,7 @@ static QualType
> >> > ConvertDeclSpecToType(TypeProcessingState &state) {
> >> > // "At least one type specifier shall be given in the
declaration
> >> > // specifiers in each declaration, and in the
specifier-qualifier
> >> > list in
> >> > // each struct declaration and type name."
> >> > - // FIXME: Does Microsoft really have the implicit int
extension
> >> > in
> >> > C++?
> >> > - if (S.getLangOpts().CPlusPlus &&
> >> > - !S.getLangOpts().MicrosoftExt) {
> >> > + if (S.getLangOpts().CPlusPlus) {
> >> > S.Diag(DeclLoc, diag::err_missing_type_specifier)
> >> > << DS.getSourceRange();
> >> >
> >> > diff --git a/test/Rewriter/rewrite-byref-in-nested-blocks.mm
> >> > b/test/Rewriter/rewrite-byref-in-nested-blocks.mm
> >> > index 022bb5f..f416b66 100644
> >> > --- a/test/Rewriter/rewrite-byref-in-nested-blocks.mm
> >> > +++ b/test/Rewriter/rewrite-byref-in-nested-blocks.mm
> >> > @@ -19,7 +19,7 @@ void f(void (^block)(void));
> >> > - (void)foo {
> >> > __block int kerfluffle;
> >> > // radar 7692183
> >> > - __block x;
> >> > + __block int x;
> >> > f(^{
> >> > f(^{
> >> > y = 42;
> >> >
> >> > diff --git a/test/Sema/MicrosoftCompatibility.cpp
> >> > b/test/Sema/MicrosoftCompatibility.cpp
> >> > new file mode 100644
> >> > index 0000000..15c2558
> >> > --- /dev/null
> >> > +++ b/test/Sema/MicrosoftCompatibility.cpp
> >> > @@ -0,0 +1,4 @@
> >> > +// RUN: %clang_cc1 %s -fsyntax-only -Wno-unused-value -Wmicrosoft
> >> > -verify
> >> > -fms-compatibility
> >> > +
> >> > +// PR15845
> >> > +int foo(xxx); // expected-error{{unknown type name}}
> >> >
> >> >
> >> > --
> >> > Thanks,
> >> > --Serge
> >> >
> >> > _______________________________________________
> >> > cfe-commits mailing list
> >> > cfe-commits at cs.uiuc.edu
> >> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
> >> >
> >
> >
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