Re: [PATCH c++ 06/12] Fix constness problem in ioscm_make_gdb_stdio_port

[Doug Evans <xdje42@gmail.com>]

Simon Marchi <simon.marchi@polymtl.ca> writes:
> ioscm_make_gdb_stdio_port passes const char pointers (literal strings) to
> scm_mode_bits, which takes a non-const char pointer.  Ideally, we would
> change scm_mode_bits to take a const char pointer, but it's not part of
> an API we control.
>
> Instead, it's easy enough to build the string to pass to scm_mode_bits in
> a (non-const) char array and pass that.
>
> gdb/ChangeLog:
>
> 	* guile/scm-ports.c (ioscm_make_gdb_stdio_port): Pass non-const
> 	char pointer to scm_mode_bits.
> ---
>  gdb/guile/scm-ports.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/gdb/guile/scm-ports.c b/gdb/guile/scm-ports.c
> index 925f3b2..49e4fd6 100644
> --- a/gdb/guile/scm-ports.c
> +++ b/gdb/guile/scm-ports.c
> @@ -357,29 +357,38 @@ ioscm_init_stdio_buffers (SCM port, long mode_bits)
>  static SCM
>  ioscm_make_gdb_stdio_port (int fd)
>  {
> -  int is_a_tty = isatty (fd);
>    const char *name;
>    long mode_bits;
>    SCM port;
> +  char buf[3];
> +
> +  memset (buf, 0, sizeof (buf));
>  
>    switch (fd)
>      {
>      case 0:
>        name = input_port_name;
> -      mode_bits = scm_mode_bits (is_a_tty ? "r0" : "r");
> +      buf[0] = 'r';
>        break;
>      case 1:
>        name = output_port_name;
> -      mode_bits = scm_mode_bits (is_a_tty ? "w0" : "w");
> +      buf[0] = 'w';
>        break;
>      case 2:
>        name = error_port_name;
> -      mode_bits = scm_mode_bits (is_a_tty ? "w0" : "w");
> +      buf[0] = 'w';
>        break;
>      default:
>        gdb_assert_not_reached ("bad stdio file descriptor");
>      }
>  
> +  if (isatty (fd))
> +    {
> +      buf[1] = '0';
> +    }

Community rules say to not use braces here.
Ok with that change.

> +
> +  mode_bits = scm_mode_bits (buf);
> +
>    port = ioscm_open_port (stdio_port_desc, mode_bits);
>  
>    scm_set_port_filename_x (port, gdbscm_scm_from_c_string (name));