[Coco] Microware C question/problem

[James Jones]

Bob Devries wrote:
> besides that, the code output for "/"||"\\" is:
> ldd #1
> very odd indeed.

You can thank what optimization the compiler does. Remember what || is 
defined to do: x || y has the same result as

    x ? 1 : (y ? 1 : 0)

"/", being a string constant, evaluates to a pointer to the first 
character of the string. It's guaranteed that NULL (0) is not equal to 
the address of anything, so "/" || "\\" can be evaluated at compile time 
to the constant 1.

It looks like the original author was looking for the last character in 
the string that is either a slash or a backslash, and did the moral 
equivalent of someone who writes

   n == 2 || 3

and expects it to evaluate to 1 if n is either equal to 2 or equal to 3.

	James

> -- 
> Regards, Bob Devries, Dalby, Queensland, Australia
> 
> Isaiah 50:4 The sovereign Lord has given me
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> 
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> 
> ----- Original Message ----- From: "Robert Gault" 
> <robert.gault at worldnet.att.net>
> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> Sent: Saturday, December 31, 2005 11:33 AM
> Subject: [Coco] Microware C question/problem
> 
> 
>> I am trying to test a library function in Microware C. A very strange 
>> bug was found for which I can't find a source. Here is the library 
>> call that causes the problem. Ignore whether the C syntax is correct 
>> but just look at the resulting asm code.
>>
>> n = strrchr(*file, "/" || "\\");
>>
>> Partial output from c.pass2
>>
>>  lead _3,pcr
>>  lbne _6
>> _7
>>  lead _4,pcr
>>
>> Clearly this is not legal code because of the lead. If the || "\\" is 
>> removed from the source, the lead goes away.
>>
>> What is causing this bad asm code? It seems to be a c.pass2 problem 
>> but I've compiled some very large C programs and never seen anything 
>> like this before.
>>
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> 
>