* %d or %ld for datatype int?
@ 2003-12-22 20:23 Rich Johnson
2003-12-22 20:50 ` Eljay Love-Jensen
0 siblings, 1 reply; 3+ messages in thread
From: Rich Johnson @ 2003-12-22 20:23 UTC (permalink / raw)
To: gcc-help
Hi folks--
I'm having trouble getting the following to compile cleanly on multiple
platforms. Both platforms are using gcc 3.3:
#include <sys/time.h>
#include <stdio.h>
int main(){
struct timezone tz;
struct timeval now;
gettimeofday (&now, &tz);
printf ( "%ld seconds into the epoch\n", now.tv_sec );
return 0;
}
"gcc -Wall ..." on OSX (10.2.8) reports:
test.c: In function `main':
test.c:8: warning: long int format, int32_t arg (arg 2)
where tv_sec is an "int32_t" which is an "int" which is a 32-bit integer
If I change the "%ld" to "%d", then compilation on a linux platform
reports:
test.c: In function `main':
test.c:8: warning: long int format, __time_t arg (arg 2)
tv_sec is a "__time_t" which is a "long int" which is a 32-bit integer.
What gives here? Do I have to explicitly cast the tv_sec to a "long
int" to get a clean compilation on both platforms?
It just seems odd that in both cases the warning boils down to
"warning: 32bit integer used where 32bit integer expected"
Thanks,
--rich
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: %d or %ld for datatype int?
2003-12-22 20:23 %d or %ld for datatype int? Rich Johnson
@ 2003-12-22 20:50 ` Eljay Love-Jensen
2003-12-22 22:13 ` Rich Johnson
0 siblings, 1 reply; 3+ messages in thread
From: Eljay Love-Jensen @ 2003-12-22 20:50 UTC (permalink / raw)
To: Rich Johnson, gcc-help
Hi Rich,
Try this:
printf ( "%ld seconds into the epoch\n", (long int)now.tv_sec );
HTH,
--Eljay
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: %d or %ld for datatype int?
2003-12-22 20:50 ` Eljay Love-Jensen
@ 2003-12-22 22:13 ` Rich Johnson
0 siblings, 0 replies; 3+ messages in thread
From: Rich Johnson @ 2003-12-22 22:13 UTC (permalink / raw)
To: Eljay Love-Jensen; +Cc: gcc-help
On Monday, December 22, 2003, at 03:51 PM, Eljay Love-Jensen wrote:
> Hi Rich,
>
> Try this:
> printf ( "%ld seconds into the epoch\n", (long int)now.tv_sec );
>
Thanks, I don't know why but it takes me a bit of effort to accept the
need for a cast--especially after all the effort that went into
typedefs for int32_t, __time_t, etc.
I rationalize the cast as producing "what printf" expects rather than
what "the data is". It also helps to realize that it will work with
64-bit architectures, no matter what __time_t is defined to be.
--rich
^ permalink raw reply [flat|nested] 3+ messages in thread
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2003-12-22 20:23 %d or %ld for datatype int? Rich Johnson
2003-12-22 20:50 ` Eljay Love-Jensen
2003-12-22 22:13 ` Rich Johnson
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