Re: [PATCH v2] argp-help: Get rid of alloca.

[Joe Simmons-Talbott <josimmon@redhat.com>]

On Wed, Sep 13, 2023 at 11:39:10AM -0300, Adhemerval Zanella Netto wrote:
> 
> 
> On 28/08/23 15:27, Joe Simmons-Talbott via Libc-alpha wrote:
> > Replace alloca with a scratch_buffer to avoid potential stack overflow.
> > 
> > Checked on x86_64-linux-gnu
> > ---
> > Changes to v1:
> >  * Call assert on allocation failure.
> > 
> >  argp/argp-help.c | 30 +++++++++++++++++++++++++++---
> >  1 file changed, 27 insertions(+), 3 deletions(-)
> > 
> > diff --git a/argp/argp-help.c b/argp/argp-help.c
> > index d019ed58d2..af99649f20 100644
> > --- a/argp/argp-help.c
> > +++ b/argp/argp-help.c
> > @@ -40,6 +40,7 @@ char *alloca ();
> >  # endif
> >  #endif
> >  
> > +#include <scratch_buffer.h>
> >  #include <stdbool.h>
> >  #include <stddef.h>
> >  #include <stdlib.h>
> > @@ -1450,8 +1451,19 @@ hol_usage (struct hol *hol, argp_fmtstream_t stream)
> >      {
> >        unsigned nentries;
> >        struct hol_entry *entry;
> > -      char *short_no_arg_opts = alloca (strlen (hol->short_options) + 1);
> > -      char *snao_end = short_no_arg_opts;
> > +      struct scratch_buffer buf;
> > +      scratch_buffer_init (&buf);
> > +      char *short_no_arg_opts;
> > +      char *snao_end;
> > +      bool result;
> > +
> > +      result = scratch_buffer_set_array_size (&buf, 1,
> > +					   strlen (hol->short_options) + 1);
> > +      assert (result);
> > +
> > +      short_no_arg_opts = buf.data;
> > +      snao_end = short_no_arg_opts;
> > +	
> >  
> 
> With a second look, this interface is really not well designed for memory
> allocation failures so I think it would be simpler to just use malloc here
> and assert for allocation failure (It would also make it simpler to eventually
> sync with gnulib).
> 
> Also, remove the boilerplate alloca definition above.

Ack.  Fixed in v3.

Thanks,
Joe