Hi,
please help me understand these strict-aliasing warnings:
$ cat test.c
/* 1*/ extern void allocate(int size, void** p);
/* 2*/
/* 3*/ typedef struct X {
/* 4*/ char A;
/* 5*/ } X;
/* 6*/
/* 7*/ X* test1(void)
/* 8*/ {
/* 9*/ X *x;
/*10*/ allocate((int)sizeof(X), (void**)&x); /* current code */
/*11*/ allocate((int)sizeof(X), &x); /* as older gcc warned here already */
/*12*/ return x;
/*13*/ }
/*14*/
/*15*/ X* test2(void)
/*16*/ {
/*17*/ union {
/*18*/ X *x;
/*19*/ void* v;
/*20*/ } u;
/*21*/ allocate((int)sizeof(X), &u.v);
/*22*/ allocate((int)sizeof(X), (void**)&u);
/*23*/ return u.x;
/*24*/ }
$ gcc -Wall -O2 -c test.c -Wstrict-aliasing=2
test.c: In function 'test1':
test.c:10: warning: dereferencing type-punned pointer will break strict-aliasing rules
test.c:11: warning: passing argument 2 of 'allocate' from incompatible pointer type
test.c: In function 'test2':
test.c:22: warning: dereferencing type-punned pointer might break strict-aliasing rules
Strange is that line 10 "will", but line 22 "might" break
strict-aliasing rules.
Do I really need the union here like in test2() and line 21 ?
Or is there another "correct" way to get rid of warning in line 10 ?
Thanks!
/haubi/
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