[PATCH] Add "%d" support to _dl_debug_vdprintf

[Adhemerval Zanella]

On 09/06/2020 11:46, H.J. Lu wrote:
> On Tue, Jun 9, 2020 at 7:39 AM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>>
>> On 09/06/2020 11:18, Adhemerval Zanella wrote:
>>>
>>>
>>> On 05/06/2020 12:03, H.J. Lu via Libc-alpha wrote:
>>>> "%d" will be used to print out signed value.
>>>
>>> LGTM with some smalls nits below.
>>>
>>>> ---
>>>>  elf/dl-misc.c | 31 +++++++++++++++++++++++++++++--
>>>>  1 file changed, 29 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/elf/dl-misc.c b/elf/dl-misc.c
>>>> index ab70481fda..c82c8ae6fa 100644
>>>> --- a/elf/dl-misc.c
>>>> +++ b/elf/dl-misc.c
>>>> @@ -167,6 +167,7 @@ _dl_debug_vdprintf (int fd, int tag_p, const char *fmt, va_list arg)
>>>>        switch (*fmt)
>>>>          {
>>>>            /* Integer formatting.  */
>>>> +        case 'd':
>>>>          case 'u':
>>>>          case 'x':
>>>>            {
>>>
>>> Ok.
>>>
>>>> @@ -179,11 +180,34 @@ _dl_debug_vdprintf (int fd, int tag_p, const char *fmt, va_list arg)
>>>>  #else
>>>>              unsigned long int num = va_arg (arg, unsigned int);
>>>>  #endif
>>>> +            bool negative = false;
>>>> +            if (*fmt == 'd')
>>>> +              {
>>>> +#if LONG_MAX != INT_MAX
>>>> +                if (long_mod)
>>>> +                  {
>>>> +                    if ((long) num < 0)
>>>
>>> Full type specify on cast.
>>>
>>>> +                      negative = true;
>>>> +                  }
>>>> +                else
>>>> +                  {
>>>> +                    if ((int) num < 0)> +                     {
>>>> +                        num = (unsigned int) num;
>>>> +                        negative = true;
>>>> +                      }
>>>> +                  }
>>>> +#else
>>>> +                if ((int) num < 0)
>>>> +                  negative = true;
>>>> +#endif
>>>> +              }
>>>> +
>>>>              /* We use alloca() to allocate the buffer with the most
>>>>                 pessimistic guess for the size.  Using alloca() allows
>>>>                 having more than one integer formatting in a call.  */
>>>> -            char *buf = (char *) alloca (3 * sizeof (unsigned long int));
>>>> -            char *endp = &buf[3 * sizeof (unsigned long int)];
>>>> +            char *buf = (char *) alloca (1 + 3 * sizeof (unsigned long int));
>>>> +            char *endp = &buf[1 + 3 * sizeof (unsigned long int)];
>>>
>>> I think we can remove alloca here and use INT_STRLEN_BOUND (since the
>>> string is not '\0' bounded due the writev usage).  Something like:
>>
>> Sigh, you can't actually remove the alloca here.
> 
> Why not?  It seems to work:
> 

Because the iov uses the allocated buffer on the _dl_writev and it will
an invalid pointer if we allocate on the stack without alloca.