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From: Kaz Kylheku <847-115-0292@kylheku.com>
Newsgroups: comp.compilers
Subject: Re: Bounds checking, Optimization techniques and undefined behavior
Date: Fri, 10 May 2019 03:38:48 +0000 (UTC)
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On 2019-05-08, David Brown <david.brown@hesbynett.no> wrote:
> [I'm looking at C11 and don't see where it says you can't cast away
> const.  What am I missing?  I agree any approach here is ugly and we're
> near the limits of what you can say in C. -John]

By the way, on a tangent related to this topic, I use the following
definitions in code that compiles both as C and C++:

#ifdef __cplusplus
#define strip_qual(TYPE, EXPR) (const_cast<TYPE>(EXPR))
#define convert(TYPE, EXPR) (static_cast<TYPE>(EXPR))
#define coerce(TYPE, EXPR) (reinterpret_cast<TYPE>(EXPR))
#else
#define strip_qual(TYPE, EXPR) ((TYPE) (EXPR))
#define convert(TYPE, EXPR) ((TYPE) (EXPR))
#define coerce(TYPE, EXPR) ((TYPE) (EXPR))
#endif

When compiling as C++, I get diagnostics from the more nuanced cast
operators, which reduce to just regular C casts when compiling as C.

For instance, casting away const requires strip_qual(type, val).

That's just one way we can get the benefits of some C++ safety
without leaving C. Another example is the stronger type safety
of enumerations, and the rules around void * conversions.

--
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[Wow, that's ugly.  -John]