On 10/1/19 12:40 PM, Martin Sebor wrote:
On 9/30/19 9:40 PM, Jerry DeLisle wrote:
Copying gcc list for additional thoughts on a possible bogus warning.
On 9/29/19 9:02 AM, Jerry DeLisle wrote:
--- snip ---
In case it helps, the warning is for the access:
# .MEM_68 = VDEF <.MEM_71>
MEM[(char *)_86] = 0;
where _86 is set to
_86 = &itoa_buf + _43;
and _43 has the range [136, 17179869176]. (The warning needs to
be enhanced a bit to mention the accessed object in this case.)
itoa_buf's DECL_SIZE_UNIT evaluates to 129.
The call to btoa_big in write_b:
p = btoa_big (source, itoa_buf, len, &n);
is made with len > 16. If len > sizeof itoa_buf / 8 then it does
look like btoa_big would write past the end of itoa_buf because it
writes len * 8 bytes into it. I don't know if the function can be
called with len that large but if not, adding this just above
the call suppresses the warning.
if (len > sizeof itoa_buf / 8)
__builtin_unreachable ();
Martin
Thanks Martin, this does help me understand why the warning. Yes, len cannot be
greater than 16. I decided to just use memset in write_b where the buffer is
created to avoid the assignment that triggers the warning. Your suggestion may
likewise work. In my comments describing the warning as bogus, by bogus, I mean
"not applicable" to the situation.
I notice many warnings flying by when building gcc/gfortran. My preference would
be to clear as many off as possible so that we can actually notice warnings when
they are applicable and not miss them among a crowd of warnings.
I don't know if this makes sense to anyone and I do appreciate your response.
Jerry
