Re: errno (was: VIRUS ALERT!)

[Neil Palmer <neilp@xxxxxxxxxxx>]

From Sion Coulter ?  Haven't been vacationing at a sex change clinic in 
Denmark have you ?  ;-)

...Neil





"Sion Coulter" <shc@flybynight.com.au>
Sent by: owner-midrange-l@midrange.com
2001/06/06 22:53
Please respond to MIDRANGE-L

 
        To:     MIDRANGE-L@midrange.com
        cc: 
        Subject:        errno (was: VIRUS ALERT!)



Hello Joe,

Change the bloody topic!

You wrote:
>Does anybod have the ILE C pieces needed to allow me to retrieve the 
>"errno" parameter when using the Unix APIs?  According to the manuals, I 
>need a C module because the error is exported as "errno", which is lower 
>case and cannot be accessed by ILE RPG. 

Not strictly true.  RPG IV can access lower case exports.  For example

 * Errno in C style - imported from QC2UTIL1 service program 
D errno           S                   LIKE(int_t) IMPORT('errno') 

however, although that is syntactically correct it won't work because the 
errno variable exported from the QC2UTIL1 service program is always zero. 
Bastards!  Read on ....

>And rather than provide a "geterrno()" method in the Unix APIs, evidently 

>I'm expected to make my own.  Since I don't have the ILE C compiler, 
>that's sort of difficult, so I was wondering if anybody else had gone 
>through this step.

You are expected to create your own because the conventional wisdom is 
that 
you should be using C for this stuff.  However, you don't need to create 
it 
completely because the C runtime (which is on every system) already 
provides it.  Read on ...

You do have the C compiler.  It is on your installation CD-ROM.  You can 
install it and run it for 70 days before it dies.  It is probably worth 
installing simply so you can examine the C header files whenever you need 
to convert an include to RPG IV.  If you look at the errno.h include you 
will see that errno in C on the AS/400 is actually a function call.

                 extern int *__errno(void);
                 #define errno (*__errno())

You can prototype the function call and use it from RPG IV.  It is not as 
transparent as the C version but it works.  Here is an excerpt from my 
version of errno.h for RPG IV.  Note that you only need to address the 
errno variable once in the program so put the
                       EVAL      @errno = getErrno
in the *INZSR and then errno is always available.

 *************************************************************************
 * Definition of errno :  Slightly different from C language invocation  *
 *                        due to language semantics.  Invoke like:       *
 * CL0N01Factor1+++++++Opcode&ExtExtended-factor2+++++++++++++++++++++++ *
 *                     EVAL      @errno = getErrno                       *
 * and then test like:                                                   *
 *                     IF        errno = $EWOULDBLOCK                    *
 *                        do something about it                          *
 *                     ENDIF                                             *
 *************************************************************************
 
 * Error number returned 
D errno           S                   LIKE(int_t) BASED(@errno) 
D @errno          S               * 
 
D getErrno        PR              *   Extproc('__errno') 
 /endif 

Regards,
Simon Coulter.

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