comparison of structures

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comparison of structures
\ José Bollo (18 May 2006)
. \ Fabian Cenedese (18 May 2006)
. \ cheng long (18 May 2006)

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Subject:	comparison of structures
Group:	Gcc-help
From:	José Bollo
Date:	18 May 2006

hi,

the following C code

typedef struct {
int32_t a;
void *b;
} S;
void fs() {
char t[255];
int i;
for(i=0;i<255;i++)
t[i]=(char)(i+1);
}
int cmp1(S a1, S a2) {
return !memcmp(&a1,&a2,sizeof(S));
}
int cmp2(S a1, S a2) {
return a1.a==a2.a && a1.b==a2.b;
}
void put(S y) {
int a,b;
S x;
x=y;
a=cmp1(x,y);
b=cmp2(x,y);
printf("a=%d b=%d\n",a,b);
}
int main() {
S a;
a.a=1;
a.b=&a;
fs();
put(a);
return 0;
}

compiled for my linux x86_64 using the amd64 ABI (-march=athlon64) with gcc
3.4.4 prints "a=0 b=1"

i have seen why and it is clear to me how a such result is produced.
i think that it is not a bug and that the structure can not be compared using
'memcmp'.

do you agree or it a bug ?

regards
josé