ideally there should be no -Wunused-parameter compiler warning when the
parameter is used.
would it feel better to move the "FP" warnings about virtual functions, for
instance to clang-tidy?
> If you enable this warning, you probably want to know about unused
> parameters, independent of if your function is virtual or not, no?
imho there are some compiler warnings that are too noisy. I don't like to get a
warning when there is obviously no bug:
sign compare:
if the signed value is obviously not negative then there is no bug:
signed x; .. if (x>10 && x < s.size())
unused parameter:
could check in the current translation unit if the parameter is used in an
overloaded method.
constructor initialization order:
should not warn if the order obviously does not matter. for instance
initialization order of pod variables using constants.
etc
Best regards,
Daniel Marjamäki
..................................................................................................................
Daniel Marjamäki Senior Engineer
Evidente ES East AB Warfvinges väg 34 SE-112 51 Stockholm Sweden
Mobile: +46 (0)709 12 42 62
E-mail: [email protected]
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________________________________________
Från: [email protected] [[email protected]] för Nico Weber
[[email protected]]
Skickat: den 11 augusti 2015 20:50
Till: David Blaikie
Kopia: [email protected]; Daniel
Marjamäki; [email protected]
Ämne: Re: [PATCH] D11940: don't diagnose -Wunused-parameter in virtual method
or method that overrides base class method
On Tue, Aug 11, 2015 at 11:32 AM, David Blaikie
<[email protected]<mailto:[email protected]>> wrote:
On Tue, Aug 11, 2015 at 8:46 AM, Nico Weber via cfe-commits
<[email protected]<mailto:[email protected]>> wrote:
Can't you just change your signature to
virtual void a(int /* x */) {}
in these cases?
You could - does it add much value to do that, though?
If you enable this warning, you probably want to know about unused parameters,
independent of if your function is virtual or not, no?
(perhaps it does - it means you express the intent that the parameter is not
used and the compiler helps you check that (so that for the parameters you
think /should/ be used (you haven't commented out their name but accidentally
shadow or otherwise fail to reference, you still get a warning))
- David
On Tue, Aug 11, 2015 at 6:43 AM, Daniel Marjamäki
<[email protected]<mailto:[email protected]>> wrote:
danielmarjamaki created this revision.
danielmarjamaki added a reviewer: krememek.
danielmarjamaki added a subscriber: cfe-commits.
Don't diagnose -Wunused-parameter in methods that override other methods
because the overridden methods might use the parameter
Don't diagnose -Wunused-parameter in virtual methods because these might be
overriden by other methods that use the parameter.
Such diagnostics could be more accurately written if they are based on
whole-program-analysis that establish if such parameter is unused in all
methods.
http://reviews.llvm.org/D11940
Files:
lib/Sema/SemaDecl.cpp
test/SemaCXX/warn-unused-parameters.cpp
Index: test/SemaCXX/warn-unused-parameters.cpp
===================================================================
--- test/SemaCXX/warn-unused-parameters.cpp
+++ test/SemaCXX/warn-unused-parameters.cpp
@@ -32,3 +32,20 @@
auto l = [&t...]() { return sizeof...(s); };
return l();
}
+
+// Don't diagnose virtual methods or methods that override base class
+// methods.
+class Base {
+public:
+ virtual void f(int x);
+};
+
+class Derived : public Base {
+public:
+ // Don't warn in overridden methods.
+ virtual void f(int x) {}
+
+ // Don't warn in virtual methods.
+ virtual void a(int x) {}
+};
+
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -10797,8 +10797,13 @@
if (!FD->isInvalidDecl()) {
// Don't diagnose unused parameters of defaulted or deleted functions.
- if (!FD->isDeleted() && !FD->isDefaulted())
- DiagnoseUnusedParameters(FD->param_begin(), FD->param_end());
+ if (!FD->isDeleted() && !FD->isDefaulted()) {
+ // Don't diagnose unused parameters in virtual methods or
+ // in methods that override base class methods.
+ const auto MD = dyn_cast<CXXMethodDecl>(FD);
+ if (!MD || (MD->size_overridden_methods() == 0U && !MD->isVirtual()))
+ DiagnoseUnusedParameters(FD->param_begin(), FD->param_end());
+ }
DiagnoseSizeOfParametersAndReturnValue(FD->param_begin(),
FD->param_end(),
FD->getReturnType(), FD);
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