Steve Bennett <[EMAIL PROTECTED]> wrote:
> > #include <stdio.h>
> >
> > struct test1
> > {
> > char blerg[1];
> > char type[4];
> > char flibble[3];
> > char more[2];
> > } __attribute__((packed));
> >
> > _Pragma("pack(1)") struct test2
> > {
> > char blerg[1];
> > char type[4];
> > char flibble[3];
> > char more[2];
> > };
> >
> > int main (int argc, char **argv)
> > {
> > printf("sizeof(test1) is %d\n", sizeof(struct test1));
> > printf("sizeof(test2) is %d\n", sizeof(struct test2));
> >
> > return 0;
> > }
> >
> > What does this print?
>
> sizeof(test1) is 10
> sizeof(test2) is 12
So _Pragma() works the same way as #pragma.
> > What do you get from:
> >
> > printf("vers %d\n", __STDC_VERSION__):
>
> test2.c: In function 'main':
> test2.c:5: error: '__STDC_VERSION__' undeclared (first use in this function)
> test2.c:5: error: (Each undeclared identifier is reported only once
> test2.c:5: error: for each function it appears in.)
> test2.c:5: error: syntax error before ':' token
This is interesting! I tought that GCC is a bit closer to the standard.....
> > what do you get from:
> >
> > struct test1
> > {
> > char blerg[1];
> > char type[4];
> > char flibble[3];
> > char more[2];
> > char dummy[];
> > };
> >
> > int main (int argc, char **argv)
> > {
> > printf("sizeof(test1) is %d\n", sizeof(struct test1));
> >
> > return 0;
> > }
>
> sizeof(test1) is 12
This is really bad!
After reading the C-99 Standard, it turned out that the last method
is the "official" way to prevent tail padding of structures.
Could you please run the last test again but use:
#pragma pack(1)
struct test1
{
char blerg[1];
char type[4];
char flibble[3];
char more[2];
char dummy[];
};
Jörg
--
EMail:[EMAIL PROTECTED] (home) Jörg Schilling D-13353 Berlin
[EMAIL PROTECTED] (uni)
[EMAIL PROTECTED] (work) Blog: http://schily.blogspot.com/
URL: http://cdrecord.berlios.de/old/private/ ftp://ftp.berlios.de/pub/schily
