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From: "dpotapov at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/96598] New: false NULL argument warning
 [-Wanalyzer-null-argument]
Date: Thu, 13 Aug 2020 07:40:59 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96598

            Bug ID: 96598
           Summary: false NULL argument warning [-Wanalyzer-null-argument]
           Product: gcc
           Version: 10.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dpotapov at gmail dot com
  Target Milestone: ---

Created attachment 49054
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D49054&action=3Dedit
C code to demonstrate the problem

A function receives an argument that is marked as non-NULL using  __attribu=
te__
((__nonnull__ ())), and it uses this argument to invoke another function th=
at
also takes a non-NULL argument. The first invocation does NOT produce any
warning as expected, but the second one does:

test.c:67:9: warning: use of NULL =E2=80=98str=E2=80=99 where non-null expe=
cted [CWE-690]
[-Wanalyzer-null-argument]

It looks strange considering the argument has not changed anywhere in the
function. Also, it looks like the warning is triggered by defining an unrel=
ated
local variable. The warning happens only when the source code is compiled w=
ith
'-fanalyzer -fsanitize=3Dundefined'.

The attached C file demonstrates the problem.=