Re: [libvirt] [PATCH] remote_daemon_dispatch.c: typecast ARRAY_CARDINALITY() in remoteDispatchProbeURI()

[Jim Fehlig]

On 8/14/19 7:13 AM, Michal Privoznik wrote:
> Since users can enable/disable drivers at compile time, it may
> happen that @drivers array is in fact empty (in both its
> occurrences within the function). This means that
> ARRAY_CARDINALITY() returns 0UL which makes gcc unhappy because
> of loop condition:
> 
>i < ARRAY_CARDINALITY(drivers)
> 
> GCC complains that @i is unsigned and comparing an unsigned value
> against 0 is always false. However, changing the type of @i to
> ssize_t is not enough, because compiler still sees the unsigned
> zero. The solution is to typecast the ARRAY_CARDINALITY().
> 
> Signed-off-by: Michal Privoznik 
> ---
>   src/remote/remote_daemon_dispatch.c | 8 
>   1 file changed, 4 insertions(+), 4 deletions(-)

Typing the original mail and reviewing and testing this patch probably took 
longer than fixing it in the first place :-). Thanks for taking care of it!

Reviewed-by: Jim Fehlig 

Regards,
Jim

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[libvirt] [PATCH] remote_daemon_dispatch.c: typecast ARRAY_CARDINALITY() in remoteDispatchProbeURI()

[Michal Privoznik]

Since users can enable/disable drivers at compile time, it may
happen that @drivers array is in fact empty (in both its
occurrences within the function). This means that
ARRAY_CARDINALITY() returns 0UL which makes gcc unhappy because
of loop condition:

  i < ARRAY_CARDINALITY(drivers)

GCC complains that @i is unsigned and comparing an unsigned value
against 0 is always false. However, changing the type of @i to
ssize_t is not enough, because compiler still sees the unsigned
zero. The solution is to typecast the ARRAY_CARDINALITY().

Signed-off-by: Michal Privoznik 
---
 src/remote/remote_daemon_dispatch.c | 8 
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/remote/remote_daemon_dispatch.c 
b/src/remote/remote_daemon_dispatch.c
index c8e353ebd3..1bd281dd6d 100644
--- a/src/remote/remote_daemon_dispatch.c
+++ b/src/remote/remote_daemon_dispatch.c
@@ -2141,9 +2141,9 @@ remoteDispatchProbeURI(bool readonly,
 "vbox",
 # endif
 };
-size_t i;
+ssize_t i;
 
-for (i = 0; i < ARRAY_CARDINALITY(drivers) && !*probeduri; i++) {
+for (i = 0; i < (ssize_t) ARRAY_CARDINALITY(drivers) && !*probeduri; 
i++) {
 VIR_AUTOFREE(char *) daemonname = NULL;
 VIR_AUTOFREE(char *) daemonpath = NULL;
 
@@ -2187,9 +2187,9 @@ remoteDispatchProbeURI(bool readonly,
 "vz",
 # endif
 };
-size_t i;
+ssize_t i;
 
-for (i = 0; i < ARRAY_CARDINALITY(drivers) && !*probeduri; i++) {
+for (i = 0; i < (ssize_t) ARRAY_CARDINALITY(drivers) && !*probeduri; 
i++) {
 VIR_AUTOFREE(char *) sockname = NULL;
 
 if (virAsprintf(, "%s/run/libvirt/virt%sd-%s",
-- 
2.21.0

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