Re: [PATCH v2] [PATCH] KEYS: trusted: fix -Wvarags warning

[Jarkko Sakkinen]

On Mon, 22 Oct 2018, ndesaulniers@xxxxxxxxxx wrote:
> Fixes the warning reported by Clang:
> security/keys/trusted.c:146:17: warning: passing an object that
> undergoes default
>      argument promotion to 'va_start' has undefined behavior [-Wvarargs]
>        va_start(argp, h3);
>                       ^
> security/keys/trusted.c:126:37: note: parameter of type 'unsigned
> char' is declared here
> unsigned char *h2, unsigned char h3, ...)
>                               ^
> Specifically, it seems that both the C90 (4.8.1.1) and C11 (7.16.1.4)
> standards explicitly call this out as undefined behavior:
>
> The parameter parmN is the identifier of the rightmost parameter in
> the variable parameter list in the function definition (the one just
> before the ...). If the parameter parmN is declared with ... or with a
> type that is not compatible with the type that results after
> application of the default argument promotions, the behavior is
> undefined.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/41
> Link: https://www.eskimo.com/~scs/cclass/int/sx11c.html
> Suggested-by: David Laight <David.Laight@xxxxxxxxxx>
> Suggested-by: Denis Kenzior <denkenz@xxxxxxxxx>
> Suggested-by: James Bottomley <jejb@xxxxxxxxxxxxxxxxxx>
> Suggested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
> Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>

/Jarkko