Subject: Re: [PATCH] Use unsigned char to squash compiler warnings

From: Junio C Hamano <[email-masked]>
Date: Mon, 02 Mar 2015 12:29:49 -0800

Ben Walton <[email-masked]> writes:

> Sun Studio on Solaris issues warnings about improper initialization
> values being used when defining tolower_trans_tbl in
> ctype.c. tolower_trans_tbl is defined as char[], which studio's
> compiler defaults to signed char[] due to the Solaris ABI. To resolve
> this, instead of supplying -xchar or another option at build time,
> declare tolower_trans_tbl as unsigned char.  Update all appropriate
> references to the new type.
>
> Signed-off-by: Ben Walton <[email-masked]>
> ---
>  ctype.c           | 2 +-
>  git-compat-util.h | 2 +-
>  kwset.c           | 8 ++++----
>  kwset.h           | 2 +-
>  4 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/ctype.c b/ctype.c
> index 0bfebb4..fc0225c 100644
> --- a/ctype.c
> +++ b/ctype.c
> @@ -30,7 +30,7 @@ const unsigned char sane_ctype[256] = {
>  };
>  
>  /* For case-insensitive kwset */
> -const char tolower_trans_tbl[256] = {
> +const unsigned char tolower_trans_tbl[256] = {
>  	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
>  	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
>  	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,

It is not obvious from the context but later elements in this array
have values above 0x7f.  So you are saying your compiler complains
when you write:

	signed char ch = 0xff;

which sort of makes sense (because you actually are storing -1 not
255 to the variable).  Throughout our codebase (and kwset is a
borrowed code that does not count as "our" codebase ;-) we do use
unsigned when we mean we want 255 and not -1, and this patch fixes
that borrowed code to be in line with the rest.

The conversion looked good from a cursory view; I didn't check it
very carefully though.

Thanks.