[Bug libc/31286] New: glibc 2.36: Aliasing violation in libio/iovdprintf.c before refactor to internal buffers

["carlos at redhat dot com" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31286

            Bug ID: 31286
           Summary: glibc 2.36: Aliasing violation in libio/iovdprintf.c
                    before refactor to internal buffers
           Product: glibc
           Version: 2.36
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: carlos at redhat dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

In libio/iovdprintf.c in glibc 2.36 (before
8ece45e4f586abd212d1c02d74d38ef681a45600 and the conversion to internal
buffers):

 58 
 59   _IO_FINISH (&tmpfil.file);
 60 

The macro casts from the first member to the outer containing struct.

 92 /* Essentially ((TYPE *) THIS)->MEMBER, but avoiding the aliasing
 93    violation in case THIS has a different pointer type.  */
 94 #define _IO_CAST_FIELD_ACCESS(THIS, TYPE, MEMBER) \
 95   (*(_IO_MEMBER_TYPE (TYPE, MEMBER) *)(((char *) (THIS)) \
 96                                        + offsetof(TYPE, MEMBER)))

This works but some downstream pointer provenance checking tooling raises this
as an error.

It really should have been '_IO_FINISH (&tmpfil)'

-- 
You are receiving this mail because:
You are on the CC list for the bug.