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Re: Making the element type of string literals const

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On 14/08/2020 11:34, Philipp Klaus Krause wrote:
> C does not allow programs to modify a string literal.
> 
> However, for historic reasons this is not reflected in their type.
> 
> E.g. this compiled, but has undefined behaviour if ever executed:
> 
> void f(void)
> {
> 	"test"[2] = 'a';
> }
> 
> It would be more consistent is the element type for string literals
> would be const-qualified. And coding standards (e.g. MISRA) require the
> use of const-qualified types already in e.g.
> 
> const char *c = "test"; // OK
> vs.
> char *c = "test"; // Allowed by C standard, not allowed by MISRA
> 
> I don't think this change would break many recent programs. So even if
> the type of char string literals cannot be changed, such a change should
> at least be possible for string literals of other types.
> 
> Is it worth writing a proposal for C2X?
> What do you think of such a change?
> 
> Philipp
> 

It would break many programs (perhaps more old ones than new ones, but
backwards compatibility is king).  In particular, you can't then use a
string literal as a parameter to a function that has a "char *" argument.

Baring obtuse use of _Generic, I believe that a program that is correct
if string literals have "const char[]" types (like in C++) will have the
same functionality with normal "char[]" types - so the change would
affect the ease of error avoidance and checking rather than the effect
of the code.

So personally I think it would be a good thing - but I strongly doubt it
could happen.

The best alternative is to have it as a compiler switch.  gcc's
"-fwrite-strings" option does exactly this, and I use it in my own code.
 (I disagree with the naming - as it affects the semantics of the
language, it should not be a "warning" option - but that's another matter.)

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Making the element type of string literals const Philipp Klaus Krause <pkk@spth.de> - 2020-08-14 11:34 +0200
  Re: Making the element type of string literals const David Brown <david.brown@hesbynett.no> - 2020-08-14 13:43 +0200
    Re: Making the element type of string literals const Florian Weimer <fw@deneb.enyo.de> - 2020-08-14 23:41 +0200
      Re: Making the element type of string literals const David Brown <david.brown@hesbynett.no> - 2020-08-17 15:23 +0200

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