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From: shankar@hpclisp.HP.COM (Shankar Unni)
Newsgroups: comp.lang.c++
Subject: float parameters in C++; type rewriting?
Message-ID: <1000037@hpclisp.HP.COM>
Date: 17 Nov 89 23:06:23 GMT
Article-I.D.: hpclisp.1000037
Organization: Hewlett-Packard Calif. Language Lab
Lines: 29

This is about the handling of formal parameters of type "float" in C++.

The 2.0 language spec seems to imply that these floats should be treated as
floats, and that any parameter passed to such functions should be passed as
a float.

In actuality, what seems to be happening is that in the generated K&R C
code (the default), an old-style definition is put out (causing the "float"
parameter to be treated by the compiler as a double), and, in the absence
of prototypes, all actual parameters are also promoted to double.

In addition, the translator is really spotty about casting the actual
parameters to type "float" at the point of call. It sometimes does the
cast, and then again, often it does not.


The reason this is an issue is for C++ *compiler* writers (those that
generate code without going through a C compiler).

What does the language spec say about this type-rewriting? Should it
happen? It is unspecified, or does the language want to commit one way or
another (say, do what ANSI C does)?

If C++ is supposed to behave like C in this regard, where does that leave
the translator?
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Shankar Unni                                   E-Mail: 
Hewlett-Packard California Language Lab.     Internet: shankar@hpda.hp.com
Phone : (408) 447-5797                           UUCP: ...!hplabs!hpda!shankar