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qom: Clean up fragile use of error_is_set() in set() methods
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Using error_is_set(ERRP) to find out whether a function failed is
either wrong, fragile, or unnecessarily opaque.  It's wrong when ERRP
may be null, because errors go undetected when it is.  It's fragile
when proving ERRP non-null involves a non-local argument.  Else, it's
unnecessarily opaque (see commit 84d18f0).

I guess the error_is_set(errp) in the ObjectProperty set() methods are
merely fragile right now, because I can't find a call chain that
passes a null errp argument.

Make the code more robust and more obviously correct: receive the
error in a local variable, then propagate it through the parameter.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
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@afaerber
Markus Armbruster authored and afaerber committed May 5, 2014
1 parent a7737e4 commit 65cd906
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Showing 6 changed files with 45 additions and 24 deletions.
11 changes: 7 additions & 4 deletions backends/rng.c
View file
Expand Up @@ -50,6 +50,7 @@ static void rng_backend_prop_set_opened(Object *obj, bool value, Error **errp)
{
RngBackend *s = RNG_BACKEND(obj);
RngBackendClass *k = RNG_BACKEND_GET_CLASS(s);
Error *local_err = NULL;

if (value == s->opened) {
return;
Expand All @@ -61,12 +62,14 @@ static void rng_backend_prop_set_opened(Object *obj, bool value, Error **errp)
}

if (k->opened) {
k->opened(s, errp);
k->opened(s, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
}

if (!error_is_set(errp)) {
s->opened = value;
}
s->opened = true;
}

static void rng_backend_init(Object *obj)
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11 changes: 7 additions & 4 deletions backends/tpm.c
View file
Expand Up @@ -112,6 +112,7 @@ static void tpm_backend_prop_set_opened(Object *obj, bool value, Error **errp)
{
TPMBackend *s = TPM_BACKEND(obj);
TPMBackendClass *k = TPM_BACKEND_GET_CLASS(s);
Error *local_err = NULL;

if (value == s->opened) {
return;
Expand All @@ -123,12 +124,14 @@ static void tpm_backend_prop_set_opened(Object *obj, bool value, Error **errp)
}

if (k->opened) {
k->opened(s, errp);
k->opened(s, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
}

if (!error_is_set(errp)) {
s->opened = value;
}
s->opened = true;
}

static void tpm_backend_instance_init(Object *obj)
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11 changes: 7 additions & 4 deletions hw/core/qdev-properties.c
View file
Expand Up @@ -751,6 +751,7 @@ static void set_prop_arraylen(Object *obj, Visitor *v, void *opaque,
Property *prop = opaque;
uint32_t *alenptr = qdev_get_prop_ptr(dev, prop);
void **arrayptr = (void *)dev + prop->arrayoffset;
Error *local_err = NULL;
void *eltptr;
const char *arrayname;
int i;
Expand All @@ -764,8 +765,9 @@ static void set_prop_arraylen(Object *obj, Visitor *v, void *opaque,
name);
return;
}
visit_type_uint32(v, alenptr, name, errp);
if (error_is_set(errp)) {
visit_type_uint32(v, alenptr, name, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
if (!*alenptr) {
Expand Down Expand Up @@ -802,8 +804,9 @@ static void set_prop_arraylen(Object *obj, Visitor *v, void *opaque,
arrayprop->prop.info->get,
arrayprop->prop.info->set,
array_element_release,
arrayprop, errp);
if (error_is_set(errp)) {
arrayprop, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
}
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6 changes: 4 additions & 2 deletions hw/misc/tmp105.c
View file
Expand Up @@ -68,10 +68,12 @@ static void tmp105_set_temperature(Object *obj, Visitor *v, void *opaque,
const char *name, Error **errp)
{
TMP105State *s = TMP105(obj);
Error *local_err = NULL;
int64_t temp;

visit_type_int(v, &temp, name, errp);
if (error_is_set(errp)) {
visit_type_int(v, &temp, name, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
if (temp >= 128000 || temp < -128000) {
Expand Down
6 changes: 4 additions & 2 deletions hw/virtio/virtio-balloon.c
View file
Expand Up @@ -142,10 +142,12 @@ static void balloon_stats_set_poll_interval(Object *obj, struct Visitor *v,
Error **errp)
{
VirtIOBalloon *s = opaque;
Error *local_err = NULL;
int64_t value;

visit_type_int(v, &value, name, errp);
if (error_is_set(errp)) {
visit_type_int(v, &value, name, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}

Expand Down
24 changes: 16 additions & 8 deletions target-i386/cpu.c
View file
Expand Up @@ -1300,10 +1300,12 @@ static void x86_cpuid_version_set_family(Object *obj, Visitor *v, void *opaque,
CPUX86State *env = &cpu->env;
const int64_t min = 0;
const int64_t max = 0xff + 0xf;
Error *local_err = NULL;
int64_t value;

visit_type_int(v, &value, name, errp);
if (error_is_set(errp)) {
visit_type_int(v, &value, name, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
if (value < min || value > max) {
Expand Down Expand Up @@ -1339,10 +1341,12 @@ static void x86_cpuid_version_set_model(Object *obj, Visitor *v, void *opaque,
CPUX86State *env = &cpu->env;
const int64_t min = 0;
const int64_t max = 0xff;
Error *local_err = NULL;
int64_t value;

visit_type_int(v, &value, name, errp);
if (error_is_set(errp)) {
visit_type_int(v, &value, name, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
if (value < min || value > max) {
Expand Down Expand Up @@ -1375,10 +1379,12 @@ static void x86_cpuid_version_set_stepping(Object *obj, Visitor *v,
CPUX86State *env = &cpu->env;
const int64_t min = 0;
const int64_t max = 0xf;
Error *local_err = NULL;
int64_t value;

visit_type_int(v, &value, name, errp);
if (error_is_set(errp)) {
visit_type_int(v, &value, name, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
if (value < min || value > max) {
Expand Down Expand Up @@ -1511,10 +1517,12 @@ static void x86_cpuid_set_tsc_freq(Object *obj, Visitor *v, void *opaque,
X86CPU *cpu = X86_CPU(obj);
const int64_t min = 0;
const int64_t max = INT64_MAX;
Error *local_err = NULL;
int64_t value;

visit_type_int(v, &value, name, errp);
if (error_is_set(errp)) {
visit_type_int(v, &value, name, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
if (value < min || value > max) {
Expand Down

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