comp.lang.c++ - 25 new messages in 13 topics - digest

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* Weird warning about data type range - 3 messages, 3 authors
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* "might be used uninitialized..." what? - 2 messages, 2 authors
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==============================================================================
TOPIC: Weird warning about data type range
http://groups.google.com/group/comp.lang.c++/t/c0fda54bd4ba1f60?hl=en
==============================================================================

== 1 of 3 ==
Date: Sat, Aug 29 2009 5:12 am
From: Stuart Golodetz

SG wrote:
> On 29 Aug., 13:20, Stuart Golodetz <b...@blah.com> wrote:
>> Note it doesn't say anything about the entire if condition, just about a
>> particular comparison (specifically the c <= 127 one). It would seem
>> that char is signed by default on your platform. To get rid of the
>> warning, just delete the second comparison, i.e. change to using:
>>
>> if(c >= 110)
>
> That's not really satisfactory if you want your code to be portable
> and support CHAR_MAX>127 cases. I'm not really interested in whether
> the compiler figured out that it can ignore the c<=127 test because
> the standard doesn't guarantee CHAR_MAX to be 127. CHAR_MAX can be
> larger.
>
> I do appreciate warnings, though. A warning in cases like
>
> unsigned foo = getfoo();
> if (foo>=0) {
> // ...
> }
>
> is totally fine because foo can never be negative regardless of the
> implementation details.
>
> Cheers!
> SG

True enough. I guess we'd need to know more about the intent of the code
to write a portable version in this instance though (e.g. I can easily
make it work just by changing char c to int c, but that's not really
answering the original question). My guess intent-wise here is "test
program", but I may be wrong :-)

Cheers,
Stu

== 2 of 3 ==
Date: Sat, Aug 29 2009 7:14 am
From: Jonathan Lee

On Aug 29, 3:33 am, Digital Puer <digital_p...@hotmail.com> wrote:
> Line 7 is the comparison "c <= 127". Ok fine, that will always
> be true, but the entire if-expression may not be true since
> there is && in the expression.

Why not just #include <climits> and wrap the second half in an #if?

if (c >= 110
#if (CHAR_MAX > 127)
&& c <= 127