Why does "small" give an error about "char"?

Question

Trying to compile an open source project with both VS2010, VS2012 in x86 and x86_64 on a windows platform running QT5.4.

A file named unit.h contains a part :

[...]
// DO NOT change noscale's value. Lots of assumptions are made based on this
// value, both in the code and (more importantly) in the database.
enum unitScale
{
   noScale = -1,
   extrasmall = 0,
   small = 1, // Line that causes errors.
   medium = 2,
   large = 3,
   extralarge = 4,
   huge = 5,
   without = 1000
};
[...]

Generates

• error C2062: type 'char' unexpected
• error C3805: 'type': unexpected token, expected either '}' or a ','

I tried every trick in my hat to solve it. I removed every use of the "small" enum in the code and I still get the error. But after having removed all the uses, I rename "small" to "smallo" everything is fine. It seems to indicate name collision but a file search gives me no references in the whole project. It's not any keyword I know of.

Got any ideas?

EDIT: Thanks to very helpful comments here is an even stranger version that works. Could somebody explain?

#ifdef small // Same with just straight "#if"
#pragma message("yes")
#endif
#ifndef small
#pragma message("no") // Always prints no.
#endif

#undef small
enum unitScale
{
   noScale = -1,
   extrasmall = 0,
   small = 1,
   medium = 2,
   large = 3,
   extralarge = 4,
   huge = 5,
   without = 1000
};

EDIT 2: The pragma directive was showing yes but only in files that had previously loaded the windows.h header, and it was lost in the compiler output in a sea of no. Thanks everyone! What a quest.

Answer 1

small is a defined in rpcndr.h. It is used as datatype for MIDL.