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Re: 'static' in array-size func parm

From: Paul Eggert
Subject: Re: 'static' in array-size func parm
Date: Thu, 07 Aug 2014 17:44:00 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0

In looking into this I realized a couple of things. First, I partially addressed this problem in 2006 in gnulib's AC_C_VARARRAYS macro (sorry, I forgot about this until today). Second, the C standardization committee addressed it in a different way, in C11's __STDC_NO_VLA__ macro. So just now I fixed gnulib to do things the C11 way. RCS should be able to use the vararrays module of the updated gnulib, and then do something like this:

/* A function's argument must point to an array with at least N elements.
   Example: 'int main (int argc, char *argv[VLA_ELEMS (argc)]);'.  */
#ifdef __STDC_NO_VLA__
# define VLA_ELEMS(n)
# define VLA_ELEMS(n) static n

I prefer the name VLA_ELEMS to ARSZ_FN_PARM, as it's shorter and more mnemonic to people who are used to the standard terminology.

It might be helpful to have a gnulib module that implements VLA_ELEMS, such as in the attached patch; what do you think? (I haven't installed it.)

Attachment: 0001-vla-new-module.patch
Description: Text document

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