builtin/gc: correct total_ram calculation with HAVE_BSD_SYSCTL

The calls to sysctl() assume a 64-bit memory size for the variable
holding the value, but the actual size depends on the key name and
platform, at least for HW_PHYSMEM.

Detect any mismatched reads, and retry with a shorter variable
when needed.

Signed-off-by: Carlo Marcelo Arenas Belón <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: carenas

builtin/gc.c

@@ -517,7 +517,7 @@ 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;
+	uint64_t physical_memory;
 	int mib[2];
 	size_t length;
 
@@ -529,9 +529,16 @@ static uint64_t total_ram(void)
 # else
 	mib[1] = HW_PHYSMEM;
 # endif
-	length = sizeof(int64_t);
-	if (!sysctl(mib, 2, &physical_memory, &length, NULL, 0))
+	length = sizeof(physical_memory);
+	if (!sysctl(mib, 2, &physical_memory, &length, NULL, 0)) {
+		if (length == 4) {
+			uint32_t mem;
+
+			if (!sysctl(mib, 2, &mem, &length, NULL, 0))
+				physical_memory = mem;
+		}
 		return physical_memory;
+	}
 #elif defined(GIT_WINDOWS_NATIVE)
 	MEMORYSTATUSEX memInfo;