[PATCH] readline_simple: Fix compiler warning

[PATCH] readline_simple: Fix compiler warning

[Sascha Hauer]

char is an unsigned type. To test the getchar() return value against
negative values we have to use a signed type. Use int instead.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 lib/readline_simple.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/readline_simple.c b/lib/readline_simple.c
index fcdbca41a9..2e52bfc2a0 100644
--- a/lib/readline_simple.c
+++ b/lib/readline_simple.c
@@ -44,7 +44,7 @@ int readline (const char *prompt, char *line, int len)
 	int	n = 0;				/* buffer index		*/
 	int	plen = 0;			/* prompt length	*/
 	int	col;				/* output column cnt	*/
-	char	c;
+	int	c;
 
 	/* print prompt */
 	if (prompt) {
-- 
2.29.2


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Re: [PATCH] readline_simple: Fix compiler warning

[Michael Olbrich]

On Wed, May 12, 2021 at 07:44:40AM +0200, Sascha Hauer wrote:
> char is an unsigned type.

That's incorrect. In the C standard it is explicitly undefined whether char
is signed or unsigned. gcc implements this differently depending on the
architecture. I think ARM and x86 differ here.

Michael

> To test the getchar() return value against
> negative values we have to use a signed type. Use int instead.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  lib/readline_simple.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/readline_simple.c b/lib/readline_simple.c
> index fcdbca41a9..2e52bfc2a0 100644
> --- a/lib/readline_simple.c
> +++ b/lib/readline_simple.c
> @@ -44,7 +44,7 @@ int readline (const char *prompt, char *line, int len)
>  	int	n = 0;				/* buffer index		*/
>  	int	plen = 0;			/* prompt length	*/
>  	int	col;				/* output column cnt	*/
> -	char	c;
> +	int	c;
>  
>  	/* print prompt */
>  	if (prompt) {
> -- 
> 2.29.2
> 
> 
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Re: [PATCH] readline_simple: Fix compiler warning

[Sascha Hauer]

On Wed, May 12, 2021 at 01:25:14PM +0200, Michael Olbrich wrote:
> On Wed, May 12, 2021 at 07:44:40AM +0200, Sascha Hauer wrote:
> > char is an unsigned type.
> 
> That's incorrect. In the C standard it is explicitly undefined whether char
> is signed or unsigned. gcc implements this differently depending on the
> architecture. I think ARM and x86 differ here.

Ok. I already reworded this to "char can be an unsigned type".

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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Re: [PATCH] readline_simple: Fix compiler warning

[Jules Maselbas]

FYI,

On Wed, May 12, 2021 at 03:04:30PM +0200, Sascha Hauer wrote:
> On Wed, May 12, 2021 at 01:25:14PM +0200, Michael Olbrich wrote:
> > On Wed, May 12, 2021 at 07:44:40AM +0200, Sascha Hauer wrote:
> > > char is an unsigned type.
> > 
> > That's incorrect. In the C standard it is explicitly undefined whether char
> > is signed or unsigned. gcc implements this differently depending on the
> > architecture. I think ARM and x86 differ here.
> 
> Ok. I already reworded this to "char can be an unsigned type".
You can use "singed char" if you really need it.

    There are five standard signed integer types, designated as signed char,
    short int, int, long int, and long long int.

from ISO/IEC 9899:TC2 - 6.2.5 Types

Best,
Jules


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