lclint-interest message 191

From 100045.1545@compuserve.com Fri Feb 20 19:05:34 1998
Sender: 100045.1545@compuserve.com
Date: Fri, 20 Feb 1998 22:33:11 +0100 (CET)
From: Hermann Kleier <100045.1545@compuserve.com>
Reply-To: Hermann Kleier <100045.1545@compuserve.com>
To: lclint-discussions 
Cc: Hermann Kleier 
Subject: signal function interface
Mime-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

I am confused by the function interface of `signal' and how LcLint handles
the confusion.  LcLinting the two line file

> void signal (int, void (*) (int));
> #define SIG_ERR (void (*) (int)) -1

yields (standard mode):

> LCLint 2.3i --- 15 Sep 97
> Finished LCLint checking --- no code errors found

I tried to typedef the signal handler function and to use it:

> typedef void SignalHandlerT (int);
> void signal (int, SignalHandlerT *);
> #define SIG_ERR (SignalHandlerT *) -1
 
This time the output takes some more lines:

> LCLint 2.3i --- 15 Sep 97
>
> test.c:2,19: Parameter 2 of function signal has inconsistent type:
>                 declared SignalHandlerT *, specified [function (int)
> returns void] *
>  Types are incompatible. (-type will suppress message)
>   load file posixstrict.lcd: Specification: [function (int) returns
> void]
> *
> test.c: (in macro SIG_ERR)
> test.c:3,18: Constant SIG_ERR specified as [function (int) returns void]
> *, but defined as
>                SignalHandlerT *: (SignalHandlerT *)-1
>  A function, variable or constant is redefined with a different type.
> (-incondefs will suppress
>   message)
>    load file posixstrict.lcd: Specification of SIG_ERR
>
> Finished LCLint checking --- 2 code errors found

This is much stuff.  Why that? Isn't the typedef-using file equivalent to
the 1st approach?

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Another question:

LcLint declares `signal'

>  void signal (int, void (*) (int));

to be a function taking a signal number and a pointer to a signal handler
and RETURNING NOTHING.  What about checking the successfull installation
of signal handlers?  ANSI C declares signal

> void (*signal (int sig, void (*func) (int)))(int);

to be a function taking a signal number and a pointer to a signal handler
and returning a pointer to a function taking an interger and returning
nothing (Plauger: P.J.: The Standard C Library. 1992, page 196).  This can
be used to check the installation of a signal handler:

> old_handler = signal( sig, &new_handler );

The example is from Harbison, Steele: C, A Referenece Manual. 1991, page
356.

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Any hints?

Hermann Kleier