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From: nfs@notecnirp.Princeton.EDU (Norbert Schlenker)
Newsgroups: comp.lang.c
Subject: Re: typedef vs #define
Keywords: difference
Message-ID: <24495@princeton.Princeton.EDU>
Date: 26 Feb 90 13:32:33 GMT
References: <8430@cbnewsh.ATT.COM> <752@s5.Morgan.COM>
Sender: news@princeton.Princeton.EDU
Reply-To: nfs@notecnirp.UUCP (Norbert Schlenker)
Distribution: usa
Organization: Dept. of Computer Science, Princeton University
Lines: 33

In article <752@s5.Morgan.COM> amull@Morgan.COM (Andrew P. Mullhaupt) writes:
>In article <8430@cbnewsh.ATT.COM>, em@cbnewsh.ATT.COM (edward.man) writes:
>> 
>>	The question is:
>> 
>> Consider the following two C statements:
>> 	typedef short	FLAGS
>> 	#define FLAGS	short
>> 
>> If I had two identical pieces of code, one used the "typedef" and
>> ther other "#define" as defined above, would there be any difference
>> in the compiled code? Does the C compiler handle the two differently?
>
>If your code compiles, it shouldn't result in different object code...

But beware.  If we change the question only slightly, to:

Consider the following two C statements:
 	typedef short * FLAGS
 	#define FLAGS short *
 
If I had two identical pieces of code, one used the "typedef" and
ther other "#define" as defined above, would there be any difference
in the compiled code? Does the C compiler handle the two differently?

Now there's a considerable difference between the two.  Imagine the
declaration:

FLAGS x, y;

The typedef results in (probably) what people expect, namely that both
x and y are pointers to short int.  The #define makes x a FLAGS and y
a short, probably not what you want.