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From: "StevenSun2021 at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug analyzer/109027] [13 Regression] ICE: SIGSEGV (infinite
 recursion in ana::constraint_manager::eval_condition /
 ana::constraint_manager::impossible_derived_conditions_p) with -fanalyzer
 since r13-6101-g4d3b7be281e73ecd
Date: Fri, 14 Apr 2023 21:23:59 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109027

Steven Sun <StevenSun2021 at hotmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |StevenSun2021 at hotmail d=
ot com

--- Comment #2 from Steven Sun <StevenSun2021 at hotmail dot com> ---
Created attachment 54862
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D54862&action=3Dedit
new test case

New logic introduced in r13-6101-g4d3b7be281e73ecd causes infinite recursio=
ns.
Specifically, `impossible_derived_conditions_p` will fail to escape this
recursion.

In this situation, for some `a`, `b`, we have `a+4` and `b-4` exist in
different equivalent classes (of the `m_equiv_classes`).


Then we try to compare `a =3D=3D b-4`, `impossible_derived_conditions_p` th=
en bring
us to

to check            `a =3D=3D b-4`,
we'll look at       `b =3D=3D a+4`,
since `a+4` is already in some equivalent class, we must know something abo=
ut
it.


to check          `b =3D=3D a+4`,
we'll look at     `a =3D=3D b-4`,
since `b-4` is already in some equivalent class, we must know something abo=
ut
it.

Then, it continues infinitely. We should bail this out. Also, it seems that=
 the
analyzer cannot recognize some template patterns, failing to enter any exit
paths.

This code path executes very rarely.

------------------

While trying to simplify the original test case, I discovered my new test c=
ase
is another infinite recursion but in a different code path.=