Note that the values are ints.

Doc/lib/liberrno.tex

@@ -4,6 +4,7 @@
 \renewcommand{\indexsubitem}{E(in module errno)}
 
 This module makes available standard errno system symbols.
+The value of each symbol is the corresponding integer value.
 The names and descriptions are borrowed from linux/include/errno.h,
 which should be pretty all-inclusive.  Of the following list, symbols
 that are not used on the current platform are not defined by the