[Bug libc/16950] New: mbrtowc on empty buffer returns 0, should return (size_t) -2

[Bug libc/16950] New: mbrtowc on empty buffer returns 0, should return (size_t) -2

[eggert at gnu dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16950

            Bug ID: 16950
           Summary: mbrtowc on empty buffer returns 0, should return
                    (size_t) -2
           Product: glibc
           Version: 2.19
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: eggert at gnu dot org
                CC: drepper.fsp at gmail dot com

Created attachment 7602
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7602&action=edit
demonstrate the mbrtowc-on-empty-buffer bug

Invoking mbrtowc (&wc, buf, 0, &mbs) should return (size_t) -2, because an
empty buffer's zero bytes "contribute to an incomplete but potentially valid
character", which is what POSIX says (size_t) -2 means.  However, mbrtowc
returns 0.  This is incorrect, as 0 should be returned only if the empty
buffer's zero bytes "complete the character that corresponds to the null wide
character", which is not what's happening here.

Other platforms I've tried seem to get this right, e.g., Solaris 10.

Compile and run the attached program mbrtowc-bug.c to demonstrate the bug.  It
outputs "mbrtowc (A, B, 0, D) == 0x0, should be 0xfffffffffffffffe".

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[Bug libc/16950] mbrtowc on empty buffer returns 0, should return (size_t) -2

[fweimer at redhat dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=16950

Florian Weimer <fweimer at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fweimer at redhat dot com
              Flags|                            |security?

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[Bug locale/16950] mbrtowc on empty buffer returns 0, should return (size_t) -2

[jsm28 at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=16950

Joseph Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|libc                        |locale

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