[libvirt] [PATCH] cgroup: preserve correct errno on failure

[Laine Stump]

On 02/15/2011 07:33 PM, Eric Blake wrote:
> On 02/15/2011 05:01 PM, Eric Blake wrote:
>> * src/util/cgroup.c (virCgroupSetValueStr, virCgroupGetValueStr)
>> (virCgroupRemoveRecursively): VIR_DEBUG can clobber errno.
>> (virCgroupRemove): Use VIR_DEBUG rather than DEBUG.
>> ---
>>       rc = virFileWriteStr(keypath, value, 0);
>>       if (rc<  0) {
>> -        DEBUG("Failed to write value '%s': %m", value);
>>           rc = -errno;
>> +        VIR_DEBUG("Failed to write value '%s': %m", value);
> Should we go one step further and guarantee that VIR_DEBUG() does not
> modify errno?

Yeah, that's just going a step further than what I did in commit 
17e19add "Preserve errno across calls to error reporting functions & 
VIR_FREE". Since there are cases when we want to report an error, but 
not count it as an "error", that makes sense (also it makes a lot of 
sense that instrumentation for debugging should be as non-intrusive as 
possible).