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bool defined where?

Posted on 2016-08-30
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Last Modified: 2016-11-28
Hi

what's the most standard lib that defines this for C++? and for c+11?

thanks
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Question by:LuckyLucks
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6 Comments
 

Author Comment

by:LuckyLucks
ID: 41777360
I thought is was a builtin type. But a simple snippet of code in C++ using visual studio 2008 is complaining that it is an unreferenced local variable when i do
bool myBoolVar;
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by:phoffric
ID: 41777549
By any chance did your file have a .c extension. ANSI C-language does not have bool intrinsically defined.
If you want, you can post the small snippet and we'll see if it runs it builds in different environments.
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Expert Comment

by:pepr
ID: 41780540
The bool is a keyword in C++. You cannot redefine it. If you read that in your old source, it is probably a C source -- as phoffric said. If you want to have syntactically the same bool type and true and false constants, you can add elsewhere code like this:

#ifndef __cplusplus
typedef unsigned char bool;
static const bool false = 0;
static const bool true = 1;
#endif

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The __cplusplus symbol (two underscores) is defined by the any C++ compiler for solving the situations like this. The code says: If the symbol is not defined (that is we use a C compiler [setting]), then define the bool type using the standard C way. Define also the constants. If the symbol is defined, then the lines are skipped and the built-in type and values (keywords) are used.

I did not check, whether bool became also keyword in later C standards. In such case, the above construct would colide even with C.
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Accepted Solution

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pepr earned 500 total points
ID: 41801075
Reading the second comment...
complaining that it is an unreferenced local variable when i do
bool myBoolVar;

It actually has nothing to do with "where the bool is defined" or whether it is a keyword or not. It says that the myBoolVar was declared here, and it is not used in the code. In other words, you can remove the definition. You can also try to search for all the myBoolVar string in the sources to check whether it is true.
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Expert Comment

by:phoffric
ID: 41801149
good observation pepr.
Would also have helped if the author had used the word, "warning". I took complaining too strongly as in error.
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Expert Comment

by:frankhelk
ID: 41903861
No comment has been added to this question in more than 21 days, so it is now classified as abandoned.

I have recommended this question be closed as follows:

Accept: pepr (https:#a41801075)

If you feel this question should be closed differently, post an objection and the moderators will review all objections and close it as they feel fit. If no one objects, this question will be closed automatically the way described above.

frankhelk
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