Pascal --> C question

[mcdonald at uxe.cso.uiuc.edu]

> 
> Another interesting optimization done by a VMS compiler, that competing
> vendors never thought of doing, is this.  If your C program contains
> 
>      fflush(stdout);
> 
> the VMS C compiler will optimize this into:
> 
>      if (F$MODE == INTERACTIVE)       /* if interactive run */
>         fflush(stdout);
>      else
>         printf("\n");                 /* if batch run */
> -- 
> Rahul Dhesi         UUCP:  <backbones>!{iuvax,pur-ee,uunet}!bsu-cs!dhesi


>I hope the compiler doesn't do this "optimization".  It is not correct.
>Flushing the stdio buffer should not insert a newline '\n' into the output
>stream.

>I don't know much about VMS.  Is it possible to connect two processes
>by means of a pipe fed on the inflow side by stdout?  Consider two
>processes, so connected, which send messages through the pipe, encoded
>as text.  In this case, the fflush() is required to assure that a message
>is dispatched through the pipe.  Is this application's F$MODE == INTERACTIVE?

Perhaps you should understand VMS before making such comments. You see,
VMS is not a flavor of UNIX. It is an entirely different operating system.
Its file system is entirely unlike Unix's. There are many different TYPES
of files. For certain kinds of files, outputting a \n in C will flush the
buffers, AND is REQUIRED at the end of a file. Ordinary text files absolutely
must end in a way that is indicated in C by /n. No particular character
is actually placed in a file to represent this; it is indicated by the
record structure. However, what is funny is that, by default, stdout
is NOT a standard text file in the version of VMS C that we use. I seriously
doubt that such behaviour is a bug though, as I've found that VMS C works
quite well (except that stdout is not an ordinary text file.)

Any genuine VMS gurus want to give the full explanation?

Doug McDonald