open(O_RDWR) and lseek() fail

Csaba Raduly
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 ~

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