-/* Possibly inefficient/inexact substitutes for _setjmp and _longjmp.
- Do not use sys_setjmp, as PNG supports only jmp_buf. The _longjmp
- substitute may munge the signal mask, but that should be OK here.
- MinGW (MS-Windows) uses _setjmp and defines setjmp to _setjmp in
- the system header setjmp.h; don't mess up that. */
-#ifndef HAVE__SETJMP
-# define _setjmp(j) setjmp (j)
-# define _longjmp longjmp
+/* Fast implementations of setjmp and longjmp. Although setjmp and longjmp
+ will do, POSIX _setjmp and _longjmp (if available) are often faster.
+ Do not use sys_setjmp, as PNG supports only jmp_buf.
+ It's OK if the longjmp substitute restores the signal mask. */
+#ifdef HAVE__SETJMP
+# define FAST_SETJMP(j) _setjmp (j)
+# define FAST_LONGJMP _longjmp
+#else
+# define FAST_SETJMP(j) setjmp (j)
+# define FAST_LONGJMP longjmp