[PATCH] libxlutil: avoid almost-undefined behavior

[Jan Beulich <jbeulich@xxxxxxxx>]

While only value computations of an object are disallowed in the
presence of another unsequenced side effect, at least gcc 4.3 looks to
extend this to taking the object's address. The resulting warning causes
the build to fail, because of -Werror.

While there also correct an adjacent comment.

Fixes: bdc0799fe26a ("libxlu: introduce xlu_pci_parse_spec_string()")
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/tools/libs/util/libxlu_pci.c
+++ b/tools/libs/util/libxlu_pci.c
@@ -155,9 +155,10 @@ int xlu_pci_parse_spec_string(XLU_Config
     if (!ret) {
         bdf_present = true;
 
-        /* Check whether 'vslot' if present */
+        /* Check whether 'vslot' is present */
         if (*ptr == '@') {
-            ret = parse_vslot(&pci->vdevfn, ++ptr, &ptr);
+            ++ptr;
+            ret = parse_vslot(&pci->vdevfn, ptr, &ptr);
             if (ret)
                 return ret;
         }