[GCC] Re: Bizarre warning about width of argument

[Russ Allbery]

Trevor Jenkins <trevor.jenkins@suneidesis.com> writes:

> the gcc options are slightly different but closer to those used in the
> actual system:

> gcc -c -fno-builtin -Wshadow foo.c

> producing

> riley.c:6: warning: declaration of `index' shadows global declaration
> riley.c: In function `foo':
> riley.c:7: warning: declaration of `index' shadows global declaration

> The function "index" is not defined in the C standard. However, it is
> mentioned in the string.h include file. So the question is how do we
> suppress the warning for non-standard functions whilst retaining the
> warning for functions defined in the standard?

Compile with gcc -ansi (or gcc -std=c99 or something similar, or define
_POSIX_SOURCE or _XOPEN_SOURCE, or several other ways of accomplishing the
same thing).  Then the system headers shouldn't expose those symbols.  Of
course, then you won't be able to call non-standard functions at all.

This is the really annoying part of using -Wshadow, and is the reason why
I've considered stopping using it as a regular compile option when
building things in "all warnings" mode.  It's not really clear how useful
-Wshadow is overall; most of the things it uncovers are completely
harmless, like using the names of standard functions as the names of
arguments in prototypes.  Or things like using:

    struct sockaddr_in sin;

in a file that for one reason or another includes math.h.

-- 
Russ Allbery (rra@stanford.edu)             <http://www.eyrie.org/~eagle/>