Re: [Lcms-user] Build warnings on OSX / clang

[Noel C. <NCa...@Pr...>]

Hello all,

Compiler warnings are available to show us where programmers have taken
liberties with the language, but have not acknowledged those liberties
(via a cast).  IMO, the C language implicit integer assignment rules
were a shortcoming of the language, leading to sloppy work, not a
feature.

In our projects all our code builds clean with Visual Studio's max
warning level (-Wall) and Code Analysis.  We don't allow warnings to
persist, and I honestly don't know why - other than economics - anyone
would want to set a project up to use anything less.

I don't mean to be critical of Marti's code - it's very good overall and
emits no warnings with Visual Studio 2017 on level 4 (which is better
than most source projects), but it DOES gather hundreds of warnings when
set to -Wall, many of which are of the form:

..\..\..\src\cmsgamma.c(143): warning C4365: '=': conversion from
'cmsUInt32Number' to 'int', signed/unsigned mismatch

Unfortunately, it really IS a coding error to expect an unsigned integer
to fit implicitly into a signed integer.   If you "just know" that there
can be no sign problems, then the code should reflect that.

The right solution is not to add casts, but rather to change the code so
that the data types DO match one another - or in a pinch use explicit
casts in the code (with appropriate comments) indicating that the
disparity has been noted and is expected and okay.

In the specific case identified (an unsigned 32 bit number being copied
to a signed 32 bit value) we can't know, without careful analysis of the
code, whether there can be (now, or in the future) a negative number or
positive 32 bit number larger than 2^31 passed around.  That's a gotcha
that should not be left in.

If types have to change, of course it's necessary to work out the
problems each code change could cause.   That's the cost of creating
truly good code.

The upside is that when it's done the code can be consistently compiled
with the highest warning level, which helps keep errors from creeping in
during ongoing development.

Marti, I'm willing to take a look at reducing the warning count if
you're willing to entertain putting the changes back into your sources
(as you have done in the past).

-Noel Carboni
 ProDigital Software