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Re: VR_RANGE with inverted bounds
On 10/07/2016 11:15 AM, Richard Biener wrote:
On October 7, 2016 6:49:39 PM GMT+02:00, Martin Sebor <email@example.com> wrote:
While processing the (p += i) expression below to validate the bounds
of the pointer in I call get_range_info for i (in tree-object-size.c).
The function returns the following VR_RANGE: [2147483648, -2147483649]
rather than the expected [0, 1]. Is such a range to be expected or
is it a bug?
This range is not valid (unless unsigned and you show it as signed).
Thanks. I believe it's signed but even if it was unsigned it wouldn't
be correct (correspond to the actual range of [0, 1]).
I don't have a test case that makes this manifest with an unpatched
compiler. There aren't too many places that call get_range_info
and the range only appears to be wrong between the second and third
runs of the object-size pass. After the third run the range is
correct. (I can see this with the -Wformat-length warning when
I pass the variable to sprintf and trigger a warning.)
Unless you have a suggestion for how I might be able to reproduce
it I'll go ahead and open a bug and include a minimum patch to show