Gentle Ping ! Please help in reviewing this.
On Sun, Feb 2, 2014 at 9:52 PM, suyog sarda <[email protected]> wrote: > Hi all, > > Thanks to Richard for pointing out the specifics. > > Attaching patch for PR18275. Please review and also suggest where to add > the test case. > > > -- > With regards, > Suyog Sarda > > > On Fri, Jan 31, 2014 at 12:43 AM, Richard Smith <[email protected]> wrote: > >> On Thu Jan 30 2014 at 6:21:34 AM, suyog sarda <[email protected]> >> wrote: >> >>> Ping !! Any help would be appreciated on this. >>> >>> On Thu, Jan 30, 2014 at 1:04 AM, suyog sarda <[email protected]>wrote: >>> >>> Hi, >>> >>> I was looking at bug 18275 - Incorrect const qualifier behavior in >>> definition. >>> >>> The declaration of A::f has a const. The definition doesn't. >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> *template <typename T>struct A { void f(const int);};template >>> <typename T>void A<T>::f(int x){ x = 0;}void f(){ A<float> a; >>> a.f(0);}* >>> >>> Clang produces an error: >>> >>> test.cpp:10:7: error: read-only variable is not assignable >>> x = 0; >>> ~ ^ >>> test.cpp:26:7: note: in instantiation of member function 'A<float>::f' >>> requested here >>> a.f(0); >>> ^ >>> >>> It only happens for templateclasses. In exact the same situation with a >>> regular class everything compiles well. >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> *struct B{ void f(const int);};void B::f(int x){ x = 0;} void >>> f(){ B b; b.f(0);}*GCC compiles both examples without an error. >>> >>> According to my understanding, the standard 13.1/3 states that Parameter >>> declarations that differ only in the presence or absence of const and/or >>> volatile are equivalent. That is, the const and volatile type-specifiers >>> for each parameter type are ignored when determining which function >>> is being declared, defined, or called. So clang is wrong to throw error >>> in template case. >>> >>> After following the code path for above examples, i came across function >>> name "*Sema::ActOnFunctionDeclarator*" in SemaDecl.cpp file, where >>> everytime a function is redeclared/defined, its new declaration is created ' >>> *CreateNewFunctionDecl*', and its parameters are copied in following >>> lines of code (l*ine number 6890 in SemaDecl.cpp in latest trunk >>> version*) >>> >>> >>> >>> >>> >>> >>> *for (unsigned i = 0, e = FTI.NumArgs; i != e; ++i) { ParmVarDecl >>> *Param = cast<ParmVarDecl>(FTI.ArgInfo[i].Param); >>> assert(Param->getDeclContext() != NewFD && "Was set before ?"); >>> Param->setDeclContext(NewFD); Params.push_back(Param);* >>> I couldn't find exactly where the codepath gets different for above two >>> cases. For both TC above, parameters get copied in above lines of code. Can >>> someone help in pointing out, where does the properties of function >>> parameters/variables are set and where does those properties get reset on >>> redeclaration/definition? Am i going wrong somewhere in above code analysis? >>> >>> >> The above is what happens when we parse a function declaration / >> definition, but it's not the code path taken during template instantiation. >> >> When we instantiate a class template, we instantiate declarations of all >> the member functions of that class template. When we later instantiate the >> definition of one of those functions, we do not instantiate another >> declaration (potentially with slightly different actual parameter types); >> instead, we reuse the prior declaration. >> >> Look into Sema::InstantiateFunctionDefinition, and in particular its call >> to addInstantiatedParametersToScope, to see where we reuse the prior >> parameters. >> > > > > -- > With regards, > Suyog Sarda > -- With regards, Suyog Sarda
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