Re: FreeTDS port to VMS V9.x on x86?

On 7/3/2025 9:00 PM, Craig A. Berry wrote:

 On 7/3/25 7:24 PM, Arne Vajhøj wrote:

On 7/3/2025 6:31 PM, Craig A. Berry wrote:

https://github.com/FreeTDS/freetds/blob/Branch-1_5/src/replacements/ vasprintf.c
>
does the following:
>
#if HAVE_PATHS_H
#include <paths.h>
#endif /* HAVE_PATHS_H */
. . .
#ifndef _PATH_DEVNULL
#define _PATH_DEVNULL "/dev/null"
#endif
>
FreeTDS is relying on autoconf to sort out whether paths.h is available
and will only include it if HAVE_PATHS_H is defined in config.h, and
thus only defines _PATH_DEVNULL if it's known not to exist. Obviously
one should avoid making up one's own reserved identifiers and clobbering
documented and well-known names, but that's not really the same thing as
providing an implementation for one that's known to be missing. This
fallback approach could of course be added to Arne's implementation if
desired; to me it seems a lot cleaner than defining yet another macro,
which would need to be defined in terms of _PATH_DEVNULL when it exists
but otherwise not.
>
The problem for VMS is that the workaround doesn't work.  Or at least it
didn't when I was first porting FreeTDS 20+ years ago because the CRTL
at the time did not recognize '/dev/null' as a valid path.  I believe
recentish CRTLs (maybe VMS 8.x and later?) do have special case code
that translates it to the native null device.  But that wasn't
available, so I added the following line to the template from which
config.h is generated on VMS:
>
#define _PATH_DEVNULL "_NLA0:"
>
The main advantage of this approach is that it worked, and it did so
with a one-line change to a file I was already maintaining. I didn't
have to sprinkle '#ifdef __VMS' in files that already existed and were
already working on other platforms. I didn't have to create a lot of new
files, the presence of which in the repository I couldn't test without
autoconf/automake, which I didn't have access to at the time.  All of
which meant upstream maintainers were far more likely to accept my changes.

>
So you are saying that for the code to work on *nix then I need
to keep those, because having it defined in config.h is a non-*nix
thing and for *nix it only set HAVE_PATHS_H which requires the
include in this file?
>
I will update.

 I think preserving the HAVE_PATHS_H check is probably a good idea.  It
makes sure you get the correct, system-specific version of
_PATH_DEVNULL, if any.  And it preserves an existing approach to
portability that you aren't worried about so you can focus on the
vasprintf() guts.

I have updated.

I haven't done any testing of your code.  I do agree with Dan that
reducing the repeated code would be a benefit.  You don't need the first
#if because the file won't even be built if HAS_VASPRINTF is detected
during configuration.

I know. But just in case it did get called.

                      Which means for the remaining 4 cases you've got
this in all of them that could be put outside the #ifdefs, and without
any nesting:
 va_list cp;
va_copy(cp, ap);
<something1>
(len < 0) return len;
<something2>
*ret = malloc(len + 1);
if(!*ret) return -1;
return vsprintf(*ret, fmt, cp);
 where something1 is always 1-3 lines and something2 is zero or one line

There are duplicated lines.
But I still believe the one block of code per case is more readable
than common code + some case specific code + common code + some
case specific code + common code.
Also imagine if someone was to add yet another approach. Now it
is just put in the #if for the case and then write the block of
code. If mixing it would all depend on the new approach - maybe
it would fit into the existing structure, maybe it would require
changing the structure if it does not fit.
Arne