[sane-devel] Some warnings/errors - please verify your backends

[Henning Meier-Geinitz]

Hi,

On Wed, Mar 26, 2003 at 10:29:53PM +0100, Oliver Rauch wrote:
> - A lot of "unused parameter" warnings.  I saw some SANE code that does
>   "var=var;" to quell such warnings, so presumably at least some people
>   care.

Probably 99% of those are harmless, just annoying.

> - Twelve "unused variable" warnings.

Maybe #ifdef problems.

> - 13 warnings which indicate carelessness with `const': two "assignment
>   discards `const' from pointer target type" and 11 "passing arg 1 of
>   `free' discards `const' from pointer target type".  How serious SANE
>   considers these depends on how serious it is about doing real const
>   poisoning; since the gcc instructions don't say to use
>   -Wwrite-strings, presumably it's not really all that serious.

Usually that's because of something like 

sane.name = strdup (name);
[...]
free (sane.name);

To avoid these, either use 

sane.name = "some name";

or 

name = (use any method to set the name);
sane.name = name;
[...]
free (name);

> - 30 "comparison between signed and unsigned".  I consider these total
>   noise, to the point where I use -Wno-sign-compare.

I found two or three errors becasue of these warnings in my code, so
sometimes they make sense. E.g. if (result < 0) to catche errors when
result is unsigned int.

> - 133 "int format, long int arg" messages.  These will matter on
>   architectures where long and int are not the same size, like alpha or
>   sparc64.  (I suspect the successful build on NetBSD/alpha despite
>   these is because they are the last format argument, and the alpha is
>   little-endian.  On a big-endian platform like sparc64, I would expect
>   incorrect results to ensue.)

That's definitely a bug. And it's mentioned for ages in
backend-writing.txt.

> - Various other format/argument type mismatches:
> 	"canon630u-common.c", line 305: warning: unsigned int format, long unsigned
>  int arg (arg 3) "canon630u-common.c", line 331: warning: unsigned int
>  format, long unsigned int arg (arg 3) "epson.c", line 908: warning: unsigned
>  int format, long unsigned int arg (arg 3) "epson.c", line 837: warning:
>  unsigned int format, size_t arg (arg 3) "canon630u-common.c", line 239:
>  warning: unsigned int format, size_t arg (arg 4) "canon630u-common.c", line
>  261: warning: unsigned int format, size_t arg (arg 4)
> 
> - One "missing initializer".
> 
> - One call to mktemp(), which actually is broken anyway, since the
>   return value test is reversed.  (backend/bh.c line 1865.)  This and
>   the following open() should be collapsed into a call to mkstemp() to
>   avoid the race between testing for nonexistence of the file and
>   opening it - though I note the open uses O_EXCL, so losing the race
>   merely produces an unnecessary error rather than a serious bug.

Most of the warnings are known. But I hesitate to touch this code
because I don't have the equipment to test it and at least some
maintainers aren't active anymore.

> - Two "passing arg N of `...' from incompatible pointer type", both in
>   the same call:
> 	"coolscan.c", line 2641: warning: passing arg 2 of `RGBIfix16' from
>  incompatible pointer type "coolscan.c", line 2641: warning: passing arg 3 of
>  `RGBIfix16' from incompatible pointer type

Coolscan is one of those backends, there are already TODO entries for
it.


> If SANE is interested, I can try to clean these up and send in patches
> for them.  (Since it works for me, I'm not inclined to bother unless
> there's a reasonable chance SANE would actually pick up the patches.)

Please send patches. I can't gurantee that I'll apply them all but
I'll do that at least for the obvious ones for unmaintained backends.

Bye,
  Henning