Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #61671

Re: Implementing static_assert

Show all headers | View raw

On 06/05/15 21:44, jacobnavia wrote:
> I have added this useful construct to the lcc-win compiler.
> 
> Description:
> 
> #include <assert.h>
> static_assert(boolean expression, message)
> 
> The boolean expression will be evaluated at compile time.
> 
> If the "boolean expression" is true at compile time, nothing happens,
> the whole becomes a NOP (no operation).
> 
> If the boolean expression fails, the character string "message" will be
> printed in an error message. The compiler appends the failed expression
> to the message. The compilation fails and no object code is generated.
> 
> If the boolean expression can't be evaluated at compile time, the
> compiler will generate a call to the _StaticAssert function, that will
> print the error message at run time if the expression fails and exit the
> program.

I /strongly/ disapprove of the idea of turning the static assert into a
run-time call if it can't be evaluated at compile-time.  I am not as
experienced a "language lawyer" as Keith and some of the others here,
but I believe the C11 standards insist that the boolean expression be
compile-time constant - and I certainly think that /should/ be the case.
 It is in the name - it is a /static/ assertion, and should have a
/static/ effect.  So no matter what freedom the C11 standard may or may
not give, give an error message if the expression is not constant.

Conversely, I would consider turning an "old-fashioned" assert into a
static assertion if the expression is compile-time constant.

> 
> What do you think?
> 
> Commentaries welcome.
> 
> 
> 

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Implementing static_assert jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-06 21:44 +0200
  Re: Implementing static_assert Keith Thompson <kst-u@mib.org> - 2015-05-06 13:28 -0700
    Re: Implementing static_assert jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-06 22:55 +0200
      Re: Implementing static_assert Keith Thompson <kst-u@mib.org> - 2015-05-06 14:30 -0700
        Re: Implementing static_assert Martin Shobe <martin.shobe@yahoo.com> - 2015-05-06 18:07 -0500
          Re: Implementing static_assert Keith Thompson <kst-u@mib.org> - 2015-05-06 17:34 -0700
          Re: Implementing static_assert David Brown <david.brown@hesbynett.no> - 2015-05-07 09:44 +0200
      Re: Implementing static_assert Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-07 12:37 -0700
  Re: Implementing static_assert David Brown <david.brown@hesbynett.no> - 2015-05-07 10:11 +0200
    Re: Implementing static_assert Ian Collins <ian-news@hotmail.com> - 2015-05-07 22:13 +1200
      Re: Implementing static_assert jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-07 12:24 +0200
        Re: Implementing static_assert Ian Collins <ian-news@hotmail.com> - 2015-05-07 22:33 +1200
          Re: Implementing static_assert David Brown <david.brown@hesbynett.no> - 2015-05-07 14:30 +0200
    Re: Implementing static_assert Philip Lantz <prl@canterey.us> - 2015-05-07 03:53 -0700
      Re: Implementing static_assert David Brown <david.brown@hesbynett.no> - 2015-05-07 14:21 +0200
        Re: Implementing static_assert Keith Thompson <kst-u@mib.org> - 2015-05-07 09:11 -0700
          Re: Implementing static_assert James Kuyper <jameskuyper@verizon.net> - 2015-05-07 12:30 -0400
            Re: Implementing static_assert James Kuyper <jameskuyper@verizon.net> - 2015-05-07 12:55 -0400
    Re: Implementing static_assert Keith Thompson <kst-u@mib.org> - 2015-05-07 09:06 -0700
  Re: Implementing static_assert jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-07 19:43 +0200
    Re: Implementing static_assert Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-07 16:10 -0700

csiph-web