Re: short circuit evaluation

James Kuyper wrote:
CBFalconer wrote:
James Kuyper wrote:

... snip about <stdbool.h> ...

You're right - my mistake. But I mis-remembered it as a standard
typedef because it makes more sense to me that it would be a
typedef. Does anyone know why it's a macro? I suppose it might be
because you can #undef a macro, but you can't turn off a typedef.
If you want to use 'bool' as the standard macro in one part of a
translation unit, and as a user-defined identifier with an
incompatible meaning from legacy code in a later part of the same
translation unit, making 'bool' a macro allows you do so. But
that seems like too convoluted a motivation for such a choice.

Because 'bool' was not a reserved word in C90. This way you can
keep the compiler compatible with C90 source that used it, and true
and false macros, differently. Note that _Bool IS a reserved word,
but is in the implementors namespace.

How would making bool a typedef that is defined in stdbool.h cause a
problem for the compiler? Standard typedefs (like size_t) aren't
keywords, any more than standard macros are.

Consider a source for C90 that defines bool, true, and false. If
C99 made those words reserved, the C90 source could not be compiled
on a C99 compiler (barring identical definitions). However, simply
failing to #include <stdbool.h> avoids the whole problem. This is
fairly automatic, since <stdbool.h> didn't exist in C90.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
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Relevant Pages

  • Re: short circuit evaluation
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    (comp.lang.c)
  • Re: short circuit evaluation
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    (comp.lang.c)
  • Re: short circuit evaluation
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    (comp.lang.c)
  • Re: short circuit evaluation
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    (comp.lang.c)
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