[PATCH v2] builtin/gc: protect against sysctl() failure in total_ram

["Carlo Marcelo Arenas Belón" <carenas@gmail.com>]

In the unlikely scenario that sysctl() fails, and uninitialized
value could be returned.

Initialize the variable used and make sure its expected size
was correct before using it.

While at it, add a cast for consistency.

Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
---
V1 would regress FreeBSD, so instead make sure that the obsoleted name isn't
used in OpenBSD/NetBSD instead

 builtin/gc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 845876ff02..3958707feb 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -539,7 +539,7 @@ static uint64_t total_ram(void)
 		return total;
 	}
 #elif defined(HAVE_BSD_SYSCTL) && (defined(HW_MEMSIZE) || defined(HW_PHYSMEM) || defined(HW_PHYSMEM64))
-	int64_t physical_memory;
+	int64_t physical_memory = 0;
 	int mib[2];
 	size_t length;
 
@@ -552,8 +552,9 @@ static uint64_t total_ram(void)
 	mib[1] = HW_PHYSMEM;
 # endif
 	length = sizeof(int64_t);
-	if (!sysctl(mib, 2, &physical_memory, &length, NULL, 0))
-		return physical_memory;
+	if (!sysctl(mib, 2, &physical_memory, &length, NULL, 0) &&
+	    length == sizeof(int64_t))
+		return (uint64_t)physical_memory;
 #elif defined(GIT_WINDOWS_NATIVE)
 	MEMORYSTATUSEX memInfo;
 
-- 
2.50.0.147.gafe0d4ec5b