[libvirt] PATCH: Use -help arg with QEMU probing

[Anthony Liguori]

Jim Meyering wrote:
> "Daniel P. Berrange" <berrange at redhat.com> wrote:
>> This patch makes the code that probes QEMU args explicitly add the -help
>> argument. This works around a problem with certain KVM builds which refuse
>> to run if executed without -help, and no KVM modules are present.
> 
> Sounds obtuse enough to deserve a comment in the code.

In all fairness, it's never been well defined that the help script is 
outputted when no options are passed.  It actually is machine dependent.

When the config file support is merged, and we introduce a default 
config, it will be possible to configure QEMU to default to -net tap and 
-boot cdn.  In this case, a VM will be launched if no arguments are passed.

Regards,

Anthony Liguori

>> It also removes the set of setenv() since that changes libvirtd's environ
>> and instead uses execle() to set the child's environment
>>
>>
>> Dan
>>
>> Index: src/qemu_conf.c
>> ===================================================================
>> RCS file: /data/cvs/libvirt/src/qemu_conf.c,v
>> retrieving revision 1.64
>> diff -u -p -r1.64 qemu_conf.c
>> --- src/qemu_conf.c	15 May 2008 20:07:34 -0000	1.64
>> +++ src/qemu_conf.c	16 May 2008 14:34:42 -0000
>> @@ -447,6 +447,8 @@ static int qemudExtractVersionInfo(const
>>      }
>>
>>      if (child == 0) { /* Kid */
>> +        const char *const qemuenv[] = { "LANG=C", NULL };
>> +
>>          if (close(STDIN_FILENO) < 0)
>>              goto cleanup1;
>>          if (close(STDERR_FILENO) < 0)
>> @@ -457,8 +459,7 @@ static int qemudExtractVersionInfo(const
>>              goto cleanup1;
>>
>>          /* Just in case QEMU is translated someday.. */
>> -        setenv("LANG", "C", 1);
>> -        execl(qemu, qemu, (char*)NULL);
>> +        execle(qemu, qemu, "-help", (char*)NULL, qemuenv);
>>
>>      cleanup1:
>>          _exit(-1); /* Just in case */
> 
> ACK
>