Add warning for c++ member variable shadowing
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Wed Feb 1 15:50:49 PST 2017
+ std::set<StringRef> bases;
+ const auto baseName =
Specifier->getType()->getAsCXXRecordDecl()->getName();
Please capitalize local variable names. Also, please don't use the record
name as a key in your set; that's not guaranteed to be unique. Instead, you
could either use a set of canonical types or of canonical CXXRecordDecl*s.
+ for (const auto *Field :
Specifier->getType()->getAsCXXRecordDecl()->fields()) {
+ if ((Field->getAccess() == AS_public || Field->getAccess() ==
AS_protected) &&
+ Field->getName() == FieldName) {
Use Specifier->getType()->getAsCXXRecordDecl()->lookup(Field->getName())
here to look up the field by name, rather than walking all the fields of
all base classes and checking if each of them has the right name. You
should also check for IndirectFieldDecls, for this case:
struct A {
union { int x; float f; };
};
struct B : A {
int x;
};
+ bases.emplace(baseName);
It's more efficient to use insert rather than emplace when inserting an
element into a set.
+ Diag(Loc, diag::warn_shadow_field)
+ << FieldName << RD->getName() << baseName;
It'd be nice to add a note here pointing at the base class member that was
shadowed.
On 31 January 2017 at 19:20, James Sun <jamessun at fb.com> wrote:
> Fixed!
>
>
>
> *From: *Saleem Abdulrasool <compnerd at compnerd.org>
> *Date: *Tuesday, January 31, 2017 at 6:53 PM
>
> *To: *James Sun <jamessun at fb.com>
> *Cc: *Richard Smith <richard at metafoo.co.uk>, "cfe-commits at lists.llvm.org"
> <cfe-commits at lists.llvm.org>, Aaron Ballman <aaron at aaronballman.com>
> *Subject: *Re: Add warning for c++ member variable shadowing
>
>
>
> Hmm, the braces in the if (bases.find(...)...) are not needed.
>
>
>
> Could you also add a test case for virtual inheritance?
>
>
>
> On Mon, Jan 30, 2017 at 8:34 PM, James Sun <jamessun at fb.com> wrote:
>
> Hi Saleem
>
>
>
> Thanks for the quick response. A test case is added. It covers some
> ordinary cases as well as corner cases like multiple paths to the same base.
>
>
>
> Thanks
>
>
>
> James
>
>
>
> *From: *Saleem Abdulrasool <compnerd at compnerd.org>
> *Date: *Monday, January 30, 2017 at 6:50 PM
> *To: *James Sun <jamessun at fb.com>
> *Cc: *Richard Smith <richard at metafoo.co.uk>, "cfe-commits at lists.llvm.org"
> <cfe-commits at lists.llvm.org>, Aaron Ballman <aaron at aaronballman.com>
>
>
> *Subject: *Re: Add warning for c++ member variable shadowing
>
>
>
> I think that the patch is starting to look pretty good!
>
>
>
> Can you add some test cases for the particular cases to diagnose in a
> separate test set to ensure that we have proper coverage of the various
> cases rather than relying on the existing test cases? Something to make
> sure that we get the simple case right as well as the complex cases (e.g.
> we don't print duplicate warnings for multiple paths).
>
>
>
>
>
> On Mon, Jan 30, 2017 at 5:50 PM, James Sun <jamessun at fb.com> wrote:
>
> Hi Richard
>
>
>
> Sorry for the late reply. Thank you for giving the feedback! The updated
> version is attached. Please let me know if there is anything improper.
>
>
>
> Thanks
>
>
>
> James
>
>
>
> *From: *<metafoo at gmail.com> on behalf of Richard Smith <
> richard at metafoo.co.uk>
> *Date: *Friday, January 27, 2017 at 3:03 PM
> *To: *James Sun <jamessun at fb.com>
> *Cc: *Saleem Abdulrasool <compnerd at compnerd.org>, "
> cfe-commits at lists.llvm.org" <cfe-commits at lists.llvm.org>, Aaron Ballman <
> aaron at aaronballman.com>
>
>
> *Subject: *Re: Add warning for c++ member variable shadowing
>
>
>
> +def warn_shadow_member_variable : Warning<
>
> + "shadowed variable '%0' in type '%1' inheriting from type '%2'">,
>
>
>
> The phrasing of this is incorrect: the things you're warning about are not
> variables, they're non-static data members. Perhaps something like:
>
>
>
> "non-static data member '%0' of '%1' shadows member inherited from type
> '%2'"
>
>
>
> + InGroup<Shadow>;
>
>
>
> Would it make sense to put this in a subgroup of -Wshadow so that it can
> be controlled separately?
>
>
>
> + /// Check if there is a member variable shadowing
>
>
>
> Please end comments in a period.
>
>
>
> + void CheckShadowInheritedVariables(const SourceLocation &Loc,
>
>
>
> Likewise, 'Variables' is wrong. We would typically use the C term 'Fields'
> for these cases within Clang sources.
>
>
>
> + for (const auto &Base : DC->bases()) {
>
> + if (const auto *TSI = Base.getTypeSourceInfo())
>
> + if (const auto *BaseClass = TSI->getType()->getAsCXXRecordDecl()) {
>
> + for (const auto *Field : BaseClass->fields())
>
> + if (Field->getName() == FieldName)
>
> + Diag(Loc, diag::warn_shadow_member_variable)
>
> + << FieldName << RD->getName() << BaseClass->getName();
>
> + // Search parent's parents
>
> + CheckShadowInheritedVariables(Loc, FieldName, RD, BaseClass);
>
> + }
>
> + }
>
>
>
> Maybe we should avoid diagnosing shadowing of members that are
> inaccessible from the derived class? What about if the field name is
> ambiguous? Also, we shouldn't recurse if lookup finds something with the
> given name in this class, and ideally we would only visit each class once,
> even if it appears multiple times in a multiple-inheritance scenario.
> CXXRecordDecl::lookupInBases can handle most of these cases for you
> automatically, and will also let you build a set of paths to problematic
> base classes in case you want to report those.
>
>
>
> On 24 January 2017 at 20:52, James Sun <jamessun at fb.com> wrote:
>
> Thanks for the comments. The new version is attached.
>
> Wrt two of your questions:
>
>
>
> (1) “The description that you have on CheckShadowInheritedVariables
> isn't really the type of comments that we have in doxygen form. Im not
> sure if its in line with the rest of the code.”
>
> I’ve read through the doxygen wiki; hopefully it’s fixed; let me know if
> it’s still wrong
>
>
>
> (2) “Why are you checking that the DeclContext has a definition rather
> than the record itself?”
>
> There are cases like “struct A; struct B : A {};”, where A does not have a
> definition. The compiler will hit an assertion failure if we call A.bases()
> directly.
>
>
>
> Thanks
>
>
>
> James
>
>
>
>
>
> *From: *Saleem Abdulrasool <compnerd at compnerd.org>
> *Date: *Tuesday, January 24, 2017 at 7:10 PM
> *To: *James Sun <jamessun at fb.com>
> *Cc: *"cfe-commits at lists.llvm.org" <cfe-commits at lists.llvm.org>, Aaron
> Ballman <aaron at aaronballman.com>, Richard Smith <richard at metafoo.co.uk>
> *Subject: *Re: Add warning for c++ member variable shadowing
>
>
>
> Some more stylistic comments:
>
>
>
> The description that you have on CheckShadowInheritedVariables isn't
> really the type of comments that we have in doxygen form. Im not sure if
> its in line with the rest of the code.
>
>
>
> The ignore warning comments are restating what is in the code, please
> remove them.
>
>
>
> Could you make the header and the source file match the name?
>
>
>
> Why are you checking that the DeclContext has a definition rather than the
> record itself?
>
>
>
> Space after the <<.
>
>
>
> Don't use the cast for the check, use isa. Although, since you use the
> value later, it is probably better to write this as:
>
>
>
> if (const auto *RD = cast<CXXRecordDecl>(CurContext))
>
> CheckShadowInheritedVariabless(Loc, Name.getAsString(), RD, RD);
>
>
>
>
>
>
>
> On Tue, Jan 24, 2017 at 4:06 PM, James Sun via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
> Coding style change
>
>
>
> *From: *James Sun <jamessun at fb.com>
> *Date: *Tuesday, January 24, 2017 at 2:36 PM
> *To: *"cfe-commits at lists.llvm.org" <cfe-commits at lists.llvm.org>
> *Subject: *Add warning for c++ member variable shadowing
>
>
>
> Dear members
>
>
>
> Here is a patch (attached) to create warnings where a member variable
> shadows the one in one of its inheriting classes. For cases where we really
> don't want to shadow member variables, e.g.
>
>
>
> class a {
>
> int foo;
>
> }
>
>
>
> class b : a {
>
> int foo; // Generate a warning
>
> }
>
>
>
> This patch
>
> (1) adds a member variable shadowing checking, and
>
> (2) incorporates it to the unit tests.
>
>
>
>
>
> Comments are welcome.
>
>
>
> Thanks
>
>
>
> James
>
>
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>
>
>
>
>
> --
>
> Saleem Abdulrasool
> compnerd (at) compnerd (dot) org
>
>
>
>
>
>
>
> --
>
> Saleem Abdulrasool
> compnerd (at) compnerd (dot) org
>
>
>
>
>
> --
>
> Saleem Abdulrasool
> compnerd (at) compnerd (dot) org
>
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