[Flac-dev] FLAC_index

[Erik de Castro Lopo]

Chris Arena wrote:

> Christian Weisgerber <naddy at mips.inka.de> wrote:
> 
> > I guess the use of unsigned index variables was an accident.  Changing
> > them back to int makes FLAC pass the "thorough" test suite on amd64.
> 
> I was wondering why there isn't a FLAC_index (FLAC_index16 or FLAC_index32)
> type that would prevent someone from just "winging" it with a bad choice for
> an index to an array?

Quite honestly, I don't think having an index type is going to do anything
helpful here. Firstly, there will be times when signed indexes are needed:

    for (i = -5 ; i <= 5 ; i++) ....

and other times when unsigned indexes are needed. Furthermore, just because
you have a FLAC_idex type doesn't prevent the C compiler from automatically 
coercing a FLAC_index type to and from signed or unsigned int.

The *only* thing that will prevent these kinds of problems is enabling
as many GCC warning flags as possible, having a strict policy of always
fixing compiler warnings and using -Werror (which turns warnings into
error) during development.

For instance, for the problem of conversions/compares that mismatch
types or specifiers -Wconversion and -Wsign-compare.

For my own stuff, I consider -Wall -Wextra an absolute minimum. I 
usually add -Werror while I'm actively working on it. 

I once tried enabling warnings on the FLAC code and found a relatively
large number of warnings. I tried to fix some of them, but many were
really difficult, like casts from "const char *" to "char *" because
of API decisions and pointer aliasing warnings. I think the later 
(pointer aliasing) may actually cause the compiler to generate slower 
code because it has to avoid certain optimisations when aliasing is 
detected.

If Josh was interested in a concerted effort to increase the number of
warnings turned on by default and fix all warnings found, I would be
happy to voulnteer to help.

Cheers,
Erik
-- 
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Erik de Castro Lopo
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