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	id AA09890; Tue, 21 Jul 92 09:59:39 -0700
Message-Id: <9207211659.AA09890@postgres.Berkeley.EDU>
From: postarch (Postgres Mailing Archive)
Subject: Re: side effect
To: postgres@postgres.berkeley.edu
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Reply-To: mer@postgres.berkeley.edu
In-Reply-To: Your message of "Thu, 09 Jul 92 23:36:09 +0700."
             <9207091427.AA22234@postgres.Berkeley.EDU> 
Date: Tue, 21 Jul 92 09:59:32 PDT

you write:

> Then I tried to load the file "window.o" as following.
> 
>   load "/user/people/young/window.o" \g
> 
> But I failed, and there was a error message "link failed"
> 
> The source code "window.c" is as following.
> 
>   # include <X11/Xlib.h>
>   # include <X11/Xutil.h>
> 
>   int disp(in)
> 
>   char *in;
>   {
>     Display *d;
>     Window w;
> 
>     d=XOpenDisplay(NULL);
>     w=XCreateSimpleWindow(d,DefaultRootWindow(d),50,50,400,300,2,BlackPixel(d
 +,0),WhitePixel(d,0));
>     XMapWindow(d,w);
>     XFlush(d);
> 
>     return(1);
>   }

The answers to these questions have been tossed around on the post_questions
alias, I'm now broadcasting the final conclusions.

| When Postgres loads an object file, it links it against itself, the standard
| C runtime library and the C math library.  Other links must be done by the
| user before Postgres attempts the load - doing a preliminary load with "ld -r"
| and having postgres load *that* file should be enough, although I've never
| tried this.

> Also, I programmed another simple example using side effect.
> In this program, I wanted the backends to print the string in the screen and 
 +create file  "test" in "user/people/young" , but the backends did not in spit
 +e of no error in compiling and loading to the backends.
> Do you know the reason?  If you know, please mail to me sooner or later.
> The source code is as follows.   
> 
> 
> > more win1.c
> # include <stdio.h>
> int win()
> {
>   FILE *fp;
>   
>   fp=fopen("user/people/young/test","w");
>   printf("I am a student");  return(1);
> }

| When running postgres under the postmaster stdin and stdout are closed
| (we use up file descriptors like they are going out of style).  If you
| want to print something in the front-end you should use elog(NOTICE, "msg");
| You will have to include "utils/log.h" to get the definition of NOTICE.


Jeff Meredith
mer@postgres.berkeley.edu