| Topic: |
DEVELOP > c-Plus-Plus |
| User: |
"Don" |
| Date: |
09 Nov 2003 06:38:37 PM |
| Object: |
Problem with bool..... |
Hi NG.
I am using some C code in my CPP code, like:
extern "C" {
#include "myC_Code.h"
}
CPP Code....
................
.............
My trouble is that some of my C function uses "bool" types. Therefore I
need, in the C files, to include "stdbool.h". But then my compiler reports
an error :-(. Strangely it reports a parsing error.......
Any ideas on how to resolve this issue?
Best Regards
Don
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| User: "John Ericson" |
|
| Title: Re: Problem with bool..... |
09 Nov 2003 07:24:02 PM |
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"Don" <nono@spam.dk> wrote in message
news:bommg0$jqq$1@news.net.uni-c.dk...
Hi NG.
I am using some C code in my CPP code, like:
extern "C" {
#include "myC_Code.h"
}
CPP Code....
...............
............
<snip>
Aside from Andry's point against muddling C++ built-in type
'bool' with C typedef, macro, or whatever 'bool' _Bool, why
are you putting extern "C" around your C code?? AFAIK that's
to suppress C++ name mangling (i.e. use C linkage
conventions).
John E.
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| User: "Andrey Tarasevich" |
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| Title: Re: Problem with bool..... |
09 Nov 2003 07:06:18 PM |
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Don wrote:
I am using some C code in my CPP code, like:
extern "C" {
#include "myC_Code.h"
}
CPP Code....
...............
............
My trouble is that some of my C function uses "bool" types. Therefore I
need, in the C files, to include "stdbool.h". But then my compiler reports
an error :-(. Strangely it reports a parsing error.......
Any ideas on how to resolve this issue?
...
Since in C99 language name 'bool' is a typedef-name for built-in type
'_Bool', your C++ compiler will complain when it encounters the 'typedef
_Bool bool' definition in 'stdbool.h'. 'bool' is a keyword in C++.
Maybe in your case the problem can be solved by selectively eliminating
the '#include <stdbool.h>' directive in C++ translation units. Instead
of including 'stdbool.h' unconditionally try doing this
#ifndef __cplusplus
#include <stdbool.h>
#endif /* __cplusplus */
However, I still think that using C99's type 'bool' in dual-language
header files is a bad idea. For example, a the following declaraion
void foo(bool);
when compiled as C99 code will be interpreted as
void foo(_Bool); /* C99's '_Bool' */
and when compiled as C++ it will be interpreted as
void foo(bool); /* C++'s 'bool' */
These are two different function signatures. Strictly speaking, I don't
know what in C++ and C99 standards guarantees that such C++ declaration
will be properly matched with corresponding C definition. As far as I
know, there's no such guarantee (correct me if I'm wrong).
--
Best regards,
Andrey Tarasevich
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| User: "Andrey Tarasevich" |
|
| Title: Re: Problem with bool..... |
09 Nov 2003 07:45:30 PM |
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Andrey Tarasevich wrote:
...
Since in C99 language name 'bool' is a typedef-name for built-in type
'_Bool', your C++ compiler will complain when it encounters the 'typedef
_Bool bool' definition in 'stdbool.h'. 'bool' is a keyword in C++.
I just noticed that 'bool' in C99 is not a typedef-name but a macro. In
this case my first point is not valid in its original form. However, a
different problem will arise. The macro definition inside 'stdbool.h'
will change the meaning of token 'bool' in your C++ translation unit,
causing all 'bool's to get replaced with '_Bool' . The C++ compiler will
choke on '_Bool' because it doesn't know what it is.
My second point still stands.
--
Best regards,
Andrey Tarasevich
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| User: "John Ericson" |
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| Title: Re: Problem with bool..... |
09 Nov 2003 08:19:41 PM |
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"Andrey Tarasevich" <andreytarasevich@hotmail.com> wrote in
message news:vqtra4a97ccmeb@news.supernews.com...
Andrey Tarasevich wrote:
...
Since in C99 language name 'bool' is a typedef-name for
built-in type
'_Bool', your C++ compiler will complain when it
encounters the 'typedef
_Bool bool' definition in 'stdbool.h'. 'bool' is a
keyword in C++.
I just noticed that 'bool' in C99 is not a typedef-name
but a macro. In
this case my first point is not valid in its original
form. However, a
different problem will arise. The macro definition inside
'stdbool.h'
will change the meaning of token 'bool' in your C++
translation unit,
causing all 'bool's to get replaced with '_Bool' . The C++
compiler will
choke on '_Bool' because it doesn't know what it is.
My second point still stands.
--
Best regards,
Andrey Tarasevich
Your basic point's valid either way. ;) . I ran across
something similar recently (in C++ code, or at least the
code is compiled as C++ code), in which someone #defined
'true' and 'false' as 1 and 0, respectively. It just seems
so wrong to #define a keyword to something else, though
presumably when the code was written (in C?), 'true' and
'false' weren't keywords...
Best regards, JE
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