Date: Sun, 14 Mar 1999 20:34:37 -0500 From: "Mark S. Reichman" <mark@borg.com> Cc: Mark Turpin <mturpin@saturn.spel.com>, Freebsd-questions <freebsd-questions@FreeBSD.ORG> Subject: Re: Programming Question Message-ID: <36EC63AD.C2159EED@borg.com> References: <Pine.BSF.4.05.9903141646550.6443-100000@saturn.spel.com> <36EC34C0.13D218B4@bulinfo.net>
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Check the memory begin addresses of the char and the short
struct elements. They are separated by two bytes even
though the char is a single byte in length. Sinc struct
js is 4 bytes in length the ending address would be
4022328340 + 4 = 4022328344.
mark@slugo:~:>cc prog.c -o prog
mark@slugo:~:>./prog
short 2
int 4
long 4
char 1
float 4
double 8
js 4
Memory address begin for js 4022328340
Memory address begin for js.junk_char 4022328340
Memory address begin for js.junk_short 4022328342
---- prog.c starts here -------------------------
struct junk_struct
{
char junk_char;
short junk_short;
};
main()
{
struct junk_struct js;
printf("short %lu\n", (unsigned long) sizeof(short));
printf("int %lu\n", (unsigned long) sizeof(int));
printf("long %lu\n", (unsigned long) sizeof(long));
printf("char %lu\n", (unsigned long) sizeof(char));
printf("float %lu\n", (unsigned long) sizeof(float));
printf("double %lu\n", (unsigned long) sizeof(double));
printf("js %lu\n", (unsigned long) sizeof(js));
printf("Memory address begin for js %lu\n", (unsigned long) &js);
printf("Memory address begin for js.junk_char %lu\n", (unsigned long) &js.junk_char);
printf("Memory address begin for js.junk_short %lu\n", (unsigned long) &js.junk_short);
return 0;
}
---------- cut here -----------
Iani Brankov wrote:
>
> Mark Turpin wrote:
> >
> > I feel really silly having to ask this.
> >
> > Why does my sizeof(mystruct) come out as 4 instead of 3 ( short + char ) ?
> >
> > struct {
> > short shortvariable;
> > char charvariable;
> > } mystruct;
> >
> > sizeof(mystruct) == 4
>
> Try finding the addresses of the structure members. As I know the compiler
> aligns every variable at even address. Maybe that's the reason.
>
> --iani
>
> To Unsubscribe: send mail to majordomo@FreeBSD.org
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--
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(@ @)
+----------oOO----(_)------------------+
| Mark S. Reichman FreeBSD |
| mark@borg.com Got source? |
+------------------------oOO-----------+
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