g++: __attribute__((deprecated)) limitations

[Edward Welbourne <eddy@opera.com>]

>Submitter-Id:	net
>Originator:	Edward Welbourne
>Organization:	
>Confidential:	no
>Synopsis:	__attribute__((deprecated)) broken with inline, ignored with pure virtual, misreported after definition
>Severity:	non-critical
>Priority:	low
>Category:	c++
>Class:		rejects-legal
>Class:		sw-bug
>Release:	3.3.3 (Debian 20040401) (Debian testing/unstable)
>Environment:
System: Linux whorl 2.4.18-1-686-smp #1 SMP Sun Feb 1 04:12:27 MST 2004 i686 GNU/Linux
Architecture: i686

	
host: i486-pc-linux-gnu
build: i486-pc-linux-gnu
target: i486-pc-linux-gnu
configured with: ../src/configure -v --enable-languages=c,c++,java,f77,pascal,objc,ada,treelang --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-gxx-include-dir=/usr/include/c++/3.3 --enable-shared --with-system-zlib --enable-nls --without-included-gettext --enable-__cxa_atexit --enable-clocale=gnu --enable-debug --enable-java-gc=boehm --enable-java-awt=xlib --enable-objc-gc i486-linux
>Description:
	The __attribute__((deprecated)):
	* cannot be used with inline methods [or: the info needs to say how to do so]
	  I get a parser error if I put it in the obvious place
	* is ignored when used with a pure virtual method (though I'm pleased to see
	  it does get inherited - if I change hook's type to Derived* I *do* get
	  my warning, even without the attribute overtly on Derived::Virtue)
	* gets a report referencing the *definition* rather than the
	  *declaration* (as advertised) if the method is used after its definition.

>How-To-Repeat:
	* Save the following to a file named deprecate.cpp; make deprecated
	  will then compile it (see comment at end recording output).
	  Observe that the use of Virtue gets no warning.
	  Observe that second warning for Method() references defn, not decl.
	* Uncomment the attribute on Inline, make deprecated, see parser error.
	  It is possible to get round this; declare it with attribute in the
	  class body, then have a separate
		inline int Base::Inline() { return 0; }
	  after the class body.

class Base {
public:
    virtual int Virtue() __attribute__((deprecated)) = 0;
    int Inline() // __attribute__((deprecated)) // causes parser error
        { return 0; }
    int Method() __attribute__((deprecated)); // declaration
};

class Derived : public Base {
    /* Adding __attribute__((deprecated)) to this makes no difference, but
     * that's sensible enough: */
    int Virtue();
};
int Derived::Virtue() { return Method(); } // warning correctly references declaration
int Base::Method() { return 42; } // definition

int main(void) {
    Derived obj;
    Base *hook = &obj;
    return hook->Virtue() // no warning about Virtue !
         + hook->Method(); // warning references definition, not declaration
}

/*
make -k deprecate CXXFLAGS=-fmessage-length=0
g++ -fmessage-length=0    deprecate.cpp   -o deprecate
deprecate.cpp: In member function `virtual int Derived::Virtue()':
deprecate.cpp:14: warning: `Method' is deprecated (declared at deprecate.cpp:6)
deprecate.cpp: In function `int main()':
deprecate.cpp:21: warning: `Method' is deprecated (declared at deprecate.cpp:15)
*/

>Fix:
	Not known.