[libvirt] [PATCHv2 08/11] qemu_capabilities: QMPCommandPtr without maintaining shadow qmperr

[Jiri Denemark]

On Mon, Jul 09, 2018 at 22:56:52 -0500, Chris Venteicher wrote:
> Previously QMPCommandPtr (handle for issuing QMP commands) required an
> external char * qmperr to persist over the lifespan of QMPCommand to
> expose a QMP error string outside of QMPCommand.
> 
> Before this change, an external char *qmperr had to be maintained
> between calls to virQEMUCapsInitQMPCommandNew and
> virQEMUCapsInitQMPCommandAbort.
> 
> This change allows the qmperr pointer to be maintained within the
> QMPCommand structure avoiding the need to track and maintain the qmperr
> across a sometimes multi-function call lifespan of a QMPCommand.
> 
> Q) Should we eliminate external *qmperr completely as there seems to be
> no current use of qmperr outside the lifespan of QMPCommand in which an
> internal qmperr char pointer can persist and be used by anywhere we have
> access to the QMPCommandPtr?
> ---
>  src/qemu/qemu_capabilities.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
> index d3f2317a1d..f33152ec40 100644
> --- a/src/qemu/qemu_capabilities.c
> +++ b/src/qemu/qemu_capabilities.c
> @@ -4272,6 +4272,7 @@ struct _virQEMUCapsInitQMPCommand {
>      uid_t runUid;
>      gid_t runGid;
>      char **qmperr;
> +    char *qmperr_internal;

I'd probably call it qmperrBuffer or something similar to make it more
obvious it's the buffer for qmperr.

>      char *monarg;
>      char *monpath;
>      char *pidfile;
> @@ -4349,7 +4350,11 @@ virQEMUCapsInitQMPCommandNew(char *binary,
>  
>      cmd->runUid = runUid;
>      cmd->runGid = runGid;
> -    cmd->qmperr = qmperr;
> +
> +    if (qmperr)
> +        cmd->qmperr = qmperr; /* external storage */
> +    else
> +        cmd->qmperr = &cmd->qmperr_internal; /* cmd internal storage */
>  
>      /* the ".sock" sufix is important to avoid a possible clash with a qemu
>       * domain called "capabilities"

You don't free the internal buffer anywhere.

Jirka