Avoid implicitly declaring exit. Future compilers will not support
implicit function declarations, so this cmake probe will always fail.
Submitted upstream: <https://sourceforge.net/p/plplot/patches/37/>
diff --git a/cmake/modules/TestForHighBitCharacters.c b/cmake/modules/TestForHighBitCharacters.c
index 338cc5ef72d90719..1dbcc1c54288ea6d 100644
--- a/cmake/modules/TestForHighBitCharacters.c
+++ b/cmake/modules/TestForHighBitCharacters.c
@@ -17,6 +17,6 @@ int
int i;
for (i = 0; i < 256; i++)
if (XOR (islower (i), ISLOWER (i)) || toupper (i) != TOUPPER (i))
- exit(1);
- exit (0);
+ return 1;
+ return 0;
}