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Re: [libvirt] [v3] API: Improve log for domain related APIs



于 2011年01月07日 00:50, Eric Blake 写道:
On 01/06/2011 08:43 AM, Osier Yang wrote:
Add VM name/UUID in log for domain related APIs.
Format: "dom=%p, (VM: name=%s, uuid=%s), param0=%s, param1=%s

*src/libvirt.c (introduce two macros: VIR_DOMAIN_DEBUG, and
VIR_DOMAIN_DEBUG0)
---
  src/libvirt.c |  243 +++++++++++++++++++++++++++++++++++++++-----------------
  1 files changed, 169 insertions(+), 74 deletions(-)

diff --git a/src/libvirt.c b/src/libvirt.c
index ee2495a..bdf9896 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -312,6 +312,39 @@ static struct gcry_thread_cbs virTLSThreadImpl = {
      NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
  };

+#define VIR_DOMAIN_DEBUG(dom, fmt, ...) {                     \
+    do {                                                      \

No need to use both an outer '{}' and an inner 'do {}while(0);'.  The
more idiomatic expression is do{}while(0) (note the missing trailing ;
in the macro definition, since it is supplied instead by the statement
where the macro is used - you had one caller that missed this) and no
extra {} (if there is any worry about ever using this as a one-line
statement in a brace-less if statement, then it is essential to let the
caller supply a trailing ; without it expanding into two statements).

But in this case, we can go one step further - VIR_DOMAIN_DEBUG is
always called at the top level (never part of a compound statement), and
we require C99 (decl-after-statement is not an issue even if
VIR_DOMAIN_DEBUG(); is not the first statement), so we can avoid
introducing a new scope altogether.  We already use compiler warnings to
ensure we don't accidentally shadow any variables, but we can be even
safer by making the macro-specific declarations less likely to collide.

+            virUUIDFormat(dom->uuid, uuidstr);                \

Just in case dom is complex, we're safer to properly parenthesize within
the macro (although I don't think any of the existing uses of dom are
complex).

+#define VIR_DOMAIN_DEBUG0(dom) {                              \

Shorter to define this as as a wrapper around VIR_DOMAIN_DEBUG, rather
than repeating logic (plus it means fewer places to touch if we change
the layout in the future).


Thanks for the detailed knowledge above.

@@ -2100,7 +2133,10 @@ error:
  virDomainPtr
  virDomainLookupByUUID(virConnectPtr conn, const unsigned char *uuid)
  {
-    DEBUG("conn=%p, uuid=%s", conn, uuid);
+    char uuidstr[VIR_UUID_STRING_BUFLEN];
+    virUUIDFormat(uuid, uuidstr);
+
+    DEBUG("conn=%p, uuid=%s", conn, uuidstr);

Good catch.  Maybe we should favor VIR_DEBUG over DEBUG, (they are
identical macros, but the latter is marked as legacy in logging.h), but
that doesn't impact this patch.

Everything else looks like straight-forward mechanical conversions.

Therefore, ACK with this squashed in (I used diff -b, to focus on the
non-indentation changes; the final patch looks better), and I'm pushing it.


Great, thanks.

Regards
Osier


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