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From: tcm@moscom.UUCP (Tom Maszerowski)
Newsgroups: comp.sys.mac.programmer
Subject: THINKC 4.0.2 #define is short
Keywords: #define preprocessor short int <<
Message-ID: <2374@moscom.UUCP>
Date: 13 Nov 90 18:11:48 GMT
Reply-To: tcm@moscom.UUCP (Tom Maszerowski)
Organization: Moscom Corp., E. Rochester, NY
Lines: 27


Here's a gotcha in THINK C 4.0.2 that got me.  It's probably in the
manual somewhere, but a cursory galnce didn't reveal it ( I couldn't
find any reference to #define or the preprocessor anywhere in the index).
Anyway, this is what happened:

given:

#define   MaxAllocation  (1<<16)

sets MaxAllocation to 0.  

I believe that this is because the preprocessor assumes that
MaxAllocation is an int ( 16 bits ) but the result of the shift is
0x10000, which requires a long ( 32 bits ).  I realize that compiler
implementers are free to make an int any size they want, but this is the
first 68000 C compiler I've used where sizeof(int) != sizeof(long).  By
replacing the shift with 0x10000, MaxAllocation was defined correctly. 
BTW, this was in code I ported, I wouldn't use this style when it's
simple to just use an explicit number. 

Is this in UMPG? I've ftp'd it but haven't printed anything yet.

-- 
Tom Maszerowski	tcm@moscom.com
		{rit,tropix,ur-valhalla}!moscom!tcm
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