open(O_RDWR) and lseek() fail
Csaba Raduly
rcsaba@gmail.com
Sat Mar 29 05:00:00 GMT 2014
On Fri, Mar 28, 2014 at 2:05 PM, Eric Blake wrote:
> On 03/28/2014 06:53 AM, Nellis, Kenneth wrote:
>> x.c:12:2: warning: format '%d' expects argument of type 'int', but argument 2 has type 'off_t' [-Wformat=]
>>
>> So, then, after changing %d to %lld, gcc -Wall -pedantic complains:
>
> My advice: You usually do NOT want to compile with -pedantic. That
> option exists for programs that are sticking _strictly_ to the C
> standard, but lseek() and off_t are not part of the C standard. There
> is no portable way to be pedantic to the C89 standard
I can be pedantic under any circumstances :)
> and simultaneously
> use 64-bit offsets. The situation is better in C99, since that
> introduced 64-bit types.
>
> If you want to use %lld, you have to use C99, not C89; use gcc -std=c99
> or gcc -std=gnu99. By omitting -std, you got gcc's default, which for
> now is still -std=c89.
>
>> Wondering how to printf an off_t value without the compiler complaining while
>> using -Wall -pedantic.
gcc -std=gnu89 -Wall -pedantic -Wno-long-long
Then you have to cast size_t into unsigned long long and off_t into
long long when printf'ing
#include <sys/types.h>
#include <stdio.h>
int main()
{
size_t x = 10;
printf("%lld\n", (long long)x);
return 0;
}
Csaba@assos ~
$ gcc -Wall -pedantic -Wno-long-long pedant.c
Csaba@assos ~
$
Csaba
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