From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 48) id 446A7398EC1C; Tue, 22 Sep 2020 14:24:34 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 446A7398EC1C From: "fweimer at redhat dot com" To: glibc-bugs@sourceware.org Subject: [Bug stdio/26649] New: printf should handle non-normal x86 long double numbers gracefully Date: Tue, 22 Sep 2020 14:24:34 +0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: new X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: glibc X-Bugzilla-Component: stdio X-Bugzilla-Version: unspecified X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: fweimer at redhat dot com X-Bugzilla-Status: NEW X-Bugzilla-Resolution: X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at sourceware dot org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: bug_id short_desc product version bug_status bug_severity priority component assigned_to reporter target_milestone Message-ID: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Bugzilla-URL: http://sourceware.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-BeenThere: glibc-bugs@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Glibc-bugs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Sep 2020 14:24:34 -0000 https://sourceware.org/bugzilla/show_bug.cgi?id=3D26649 Bug ID: 26649 Summary: printf should handle non-normal x86 long double numbers gracefully Product: glibc Version: unspecified Status: NEW Severity: normal Priority: P2 Component: stdio Assignee: unassigned at sourceware dot org Reporter: fweimer at redhat dot com Target Milestone: --- The behavior of isnan/__builtin_isnan on bit patterns that do not correspon= d to something that the CPU would produce from valid inputs is currently under-defined in the toolchain. (The GCC built-in and glibc disagree.) The isnan check in PRINTF_FP_FETCH in stdio-common/printf_fp.c assumes the = GCC behavior that returns true for non-normal numbers which are not specified as NaN. (The glibc implementation returns false for such numbers.) At present, passing non-normal numbers to __mppn_extract_long_double causes this function to produce irregularly shaped multi-precision integers, triggering undefined behavior in __printf_fp_l. With GCC 10 and glibc 2.32, this behavior is not visible because __builtin_isnan is used, which avoids calling __mppn_extract_long_double in this case. --=20 You are receiving this mail because: You are on the CC list for the bug.=