From: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
Subject: Re: [9fans] pcc limitation?
Date: Sun, 7 Nov 2010 13:32:09 +0100 [thread overview]
Message-ID: <4CD69C49.5090209@gmx.net> (raw)
In-Reply-To: <AANLkTi=6NRT9zMa8+p8mTw+uqi0PKf3wwwYnqfEA28-1@mail.gmail.com>
On 07.11.2010 05:02, Federico G. Benavento wrote:
> the syntax (){} is for structures, like (Point){0, 0} or something,
> so you don't need the braces there, just the cast
>
> .writearr = (const unsigned char*)JEDEC_WREN,
>
writearr should point to a one-member const unsigned char array, and the
zeroth element of that array has the value JEDEC_WREN.
Your suggested code has different behaviour (it casts a uchar to uchar *):
#include <stddef.h>
#include <stdio.h>
#define JEDEC_WREN 0x06
struct spi_command {
const unsigned char *writearr;
};
int main(int argc, char *argv[])
{
struct spi_command cmds[] = {
{
.writearr = (const unsigned char[]){ JEDEC_WREN },
},{
.writearr = (const unsigned char *)JEDEC_WREN,
}};
printf("Mine: writearr=%p\n", cmds[0].writearr);
printf("Mine: writearr[0]=0x%02hhx\n", cmds[0].writearr[0]);
printf("Federico: writearr=%p\n", cmds[1].writearr);
printf("Federico: writearr[0]=0x%02hhx\n", cmds[1].writearr[0]);
return 0;
}
Output is:
Mine: writearr=0xbf8eb213
Mine: writearr[0]=0x06
Federico: writearr=0x6
Segmentation fault
Regards,
Carl-Daniel
--
http://www.hailfinger.org/
next prev parent reply other threads:[~2010-11-07 12:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-07 0:56 Carl-Daniel Hailfinger
2010-11-07 4:02 ` Federico G. Benavento
2010-11-07 12:32 ` Carl-Daniel Hailfinger [this message]
2010-11-07 14:46 ` erik quanstrom
2010-11-07 16:22 ` Carl-Daniel Hailfinger
2010-11-07 18:26 ` erik quanstrom
2010-11-07 19:36 ` Carl-Daniel Hailfinger
2010-11-07 19:42 ` erik quanstrom
2010-11-08 0:16 ` Carl-Daniel Hailfinger
2010-11-08 0:56 ` erik quanstrom
2010-11-08 9:39 ` Julius Schmidt
2010-11-08 14:00 ` erik quanstrom
2010-11-08 15:17 ` Anthony Sorace
2010-11-08 2:58 ` Russ Cox
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