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use of uninitialized variable involving visit_type_uint32() and friends
From: |
Peter Maydell |
Subject: |
use of uninitialized variable involving visit_type_uint32() and friends |
Date: |
Thu, 31 Mar 2022 18:35:31 +0100 |
Coverity warns about use of uninitialized data in what seems
to be a common pattern of use of visit_type_uint32() and similar
functions. Here's an example from target/arm/cpu64.c:
static void cpu_max_set_sve_max_vq(Object *obj, Visitor *v, const char *name,
void *opaque, Error **errp)
{
ARMCPU *cpu = ARM_CPU(obj);
uint32_t max_vq;
if (!visit_type_uint32(v, name, &max_vq, errp)) {
return;
}
[code that does something with max_vq here]
}
This doesn't initialize max_vq, on the apparent assumption
that visit_type_uint32() will do so. But that function is:
bool visit_type_uint32(Visitor *v, const char *name, uint32_t *obj,
Error **errp)
{
uint64_t value;
bool ok;
trace_visit_type_uint32(v, name, obj);
value = *obj;
ok = visit_type_uintN(v, &value, name, UINT32_MAX, "uint32_t", errp);
*obj = value;
return ok;
}
So it reads the value of *obj (the uninitialized max_vq).
What's the right way to write this kind of object-property
setter function? Just pre-initialize the variable to 0?
thanks
-- PMM
- use of uninitialized variable involving visit_type_uint32() and friends,
Peter Maydell <=