Date: Fri, 8 Jun 2001 15:42:49 +0300 From: Peter Pentchev <roam@orbitel.bg> To: Thomas David Rivers <rivers@dignus.com> Cc: jhb@FreeBSD.ORG, hackers@FreeBSD.ORG Subject: Re: free() and const warnings Message-ID: <20010608154249.A7671@ringworld.oblivion.bg> In-Reply-To: <200106081055.GAA49069@lakes.dignus.com>; from rivers@dignus.com on Fri, Jun 08, 2001 at 06:55:50AM -0400 References: <20010608114957.C19938@ringworld.oblivion.bg> <200106081055.GAA49069@lakes.dignus.com>
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On Fri, Jun 08, 2001 at 06:55:50AM -0400, Thomas David Rivers wrote:
> Peter Pentchev <roam@orbitel.bg> wrote:
> >
> > On Thu, Jun 07, 2001 at 10:20:51AM -0700, John Baldwin wrote:
> > >
> > > On 07-Jun-01 Peter Pentchev wrote:
> > > > On Thu, Jun 07, 2001 at 07:07:22PM +0300, Peter Pentchev wrote:
> > > >> Hi,
> > > >>
> > > >> Is free((void *) (size_t) ptr) the only way to free a const whatever *ptr
> > > >> with WARNS=2? (or more specifically, with -Wcast-qual)
> > > >
> > > > Uhm. OK. So size_t may not be enough to hold a pointer. What is it then -
> > > > caddr_t?
> > >
> > > uintptr_t for data pointers. In theory I think code pointers may not fit in a
> > > uintptr_t.
> > >
> > > free((void *)(uintptr_t)ptr) should work.
> > >
> > > Of course, this begs the question of why you are free'ing a const. :)
> >
> > OK, here's a scenario:
> >
> > struct validation_fun {
> > const char *name;
> > valfun *fun;
> > int dyn;
> > };
> >
> > This is a structure for a set of validation functions, referenced by
> > name from another type of object. There are some predefined functions,
> > present in the code at compile-time, and hardcoded in an array, with
> > names given as "strings". Thus, the 'const'.
> >
> > However, some of the functions may be defined at runtime, with both
> > name and code sent by a server. In that case, the name is a dynamically
> > allocated char *, which needs to be freed upon cleanup. So I have:
> >
> > [cleanup function]
> > ...
> > if (val->dyn)
> > free(val->name);
> >
> > Any suggestions on how to improve the design to avoid this, if possible,
> > would be greatly welcome.
> >
> > G'luck,
> > Peter
>
> Since some strings are non-constant (the are allocated) - I believe
> the `const' qualifier in the structure declaration is incorrect.
>
> What happens if you simply don't have it in the structure declaration?
GCC complains when I try to initialize the structure with something like:
struct validation_fun val_init[] = {
{"init", valfun_init, 0}
};
This can be avoided by:
struct validation_fun val_init[] = {
{(char *) (uintptr_t) "init", valfun_init, 0}
};
..but as a matter of fact, static, pre-initialized valfun structs are
the rule rather than the exception in this program, so having this
syntax for all of them seems.. well.. ugly :)
G'luck,
Peter
--
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