[comp.std.c++] Is this code using casts valid in C++ ?

lamarche@ireq.hydro.qc.ca (Louis Lamarche) (02/05/91)

class foo { int a; };
class foob : public foo { int b; };
foo afoo;
foo* afooPtr = &afoo;
foob* afoobPtr = (foob*) afooPtr;
foo& afooRef = afoo;
foob& afoobRef = (foob&) afooRef;  // Ok with g++1.37.0, rejected by g++1.37.2-
main(){}

This code compiles well with CC 2.0 on a Sun and with Zortech 2.1, but fails
with g++1.37.2-. Is it legal ?

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rfg@NCD.COM (Ron Guilmette) (02/08/91)

In article <5217@s3.ireq.hydro.qc.ca> lamarche@ireq.hydro.qc.ca (Louis Lamarche) writes:
+class foo { int a; };
+class foob : public foo { int b; };
+foo afoo;
+foo* afooPtr = &afoo;
+foob* afoobPtr = (foob*) afooPtr;
+foo& afooRef = afoo;
+foob& afoobRef = (foob&) afooRef;  // Ok with g++1.37.0, rejected by g++1.37.2-
+main(){}
+
+This code compiles well with CC 2.0 on a Sun and with Zortech 2.1, but fails
+with g++1.37.2-. Is it legal ?

No.  That's illegal.

In your example, a `foob' is a `foo' but not vise-versa.  Thus, you may
convert a `foob&' to a `foo&' but not vise-versa.

-- 

// Ron Guilmette  -  C++ Entomologist
// Internet: rfg@ncd.com      uucp: ...uunet!lupine!rfg
// Motto:  If it sticks, force it.  If it breaks, it needed replacing anyway.