IMHO There are some misprints both in documentation and in source of 
the fontconfig.

a) In the documentation of the function FcUtf8ToUcs4 
(http://fontconfig.org/fontconfig-devel/r3058.html) there should be 
"must" instead of "nust" in this part of the text "src nust be at least 
len bytes long."

b) IMHO the name of those two functions should be 
FcConfigSetRescanInterval and FcConfigGetRescanInterval instead of 
FcConfigSetRescanInverval and FcConfigGetRescanInverval. There is "v" 
instead of "t" in the word Inverval (should be Interval). This misprint 
is in both the documentation as the source of the library. 
(http://fontconfig.org/fontconfig-devel/r1943.html)