Steps to reproduce:
This bug was reproduced with the Windows binary build of GTK+ and GIMP.  I
haven't checked if gimp-2.2.3 on Unix has the same bug.

1. Start gimp-2.2.3 Windows build (http://gimp-win.sourceforge.net/).
2. Open test.ico file (download from
<http://membled.com/work/gimp_winicon_bug/test.ico>.  It opens successfully and
the image is displayed.
3. File->Save.  A dialogue box for 'GIMP Windows Icon Plugin' appears with icon
details '8 bpp, 1-bit alpha, 256-slot palette'.
4. Press OK.
5. After a short delay the standard Windows XP crash box pops up: winicon.exe
has encountered a problem and needs to close.
6a. I pressed Debug to get a stack trace with MS Visual Studio but it was not
that helpful (see below).
6b. If you don't press Debug, the Gimp pops up a box saying: 'Plug-In crashed:
"winicon.exe" (H:\winnt\gimp\lib\gimp\2.0\plug-ins\winicon.exe)'
7. The file test.ico is truncated to zero length.  (Arguably this is a separate
bug: if the saving plugin crashes, whatever the reason, it shouldn't trash the
existing file.)

Stack trace:
>	winicon.exe!00403ea0() 	
 	ntdll.dll!7c915041() 	
 	ntdll.dll!7c91056d() 	
 	user32.dll!77d49751() 	
 	ntdll.dll!7c910833() 	
 	ntdll.dll!7c910833() 	
 	user32.dll!77d497e4() 	
 	user32.dll!77d49812() 	
 	user32.dll!77d4a555() 	
 	user32.dll!77d70494() 	
 	user32.dll!77d49812() 	
 	user32.dll!77d4a56c() 	
 	user32.dll!77d4a58d() 	
 	comctl32.dll!5d0b150e() 	
 	user32.dll!77d49b60() 	
 	user32.dll!77d49d5a() 	
 	user32.dll!77d70494() 	
 	ntdll.dll!7c90d592() 	
 	ntdll.dll!7c910f46() 	
 	ntdll.dll!7c910e91() 	
 	ntdll.dll!7c91056d() 	
 	ntdll.dll!7c910945() 	
 	ntdll.dll!7c91440e() 	
 	ntdll.dll!7c910970() 	
 	ntdll.dll!7c914481() 	
 	ntdll.dll!7c919bd3() 	
 	ntdll.dll!7c915041() 	
 	ntdll.dll!7c915233() 	
 	ntdll.dll!7c9155c9() 	
 	ntdll.dll!7c915d7d() 	
 	ntdll.dll!7c915db4() 	
 	ntdll.dll!7c9153f5() 	
 	ntdll.dll!7c918b95() 	
 	ntdll.dll!7c90f0aa() 	
 	ntdll.dll!7c918c4f() 	
 	ntdll.dll!7c918c58() 	
 	kernel32.dll!7c814d1e() 	
 	kernel32.dll!7c814d58() 	
 	kernel32.dll!7c814d63() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c9106ab() 	
 	ntdll.dll!7c911538() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c911538() 	
 	ntdll.dll!7c911596() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c91cbf2() 	
 	ntdll.dll!7c9161c2() 	
 	ntdll.dll!7c91652e() 	
 	ntdll.dll!7c91657e() 	
 	ntdll.dll!7c9105c8() 	
 	ntdll.dll!7c910551() 	
 	ntdll.dll!7c91056d() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c9106ab() 	
 	ntdll.dll!7c9106eb() 	
 	msvcrt.dll!77c42d17() 	
 	ntdll.dll!7c917e77() 	
 	ntdll.dll!7c917c0c() 	
 	ntdll.dll!7c917bf5() 	
 	ntdll.dll!7c917bb0() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c9106ab() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c910833() 	
 	kernel32.dll!7c814e12() 	
 	kernel32.dll!7c81c32e() 	
 	ntdll.dll!7c9105c8() 	
 	ntdll.dll!7c910551() 	
 	ntdll.dll!7c91056d() 	
 	ntdll.dll!7c9105c8() 	
 	ntdll.dll!7c910551() 	
 	ntdll.dll!7c91056d() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c910732() 	
 	msvcrt.dll!77c423ac() 	
 	msvcrt.dll!77c42d17() 	
 	ntdll.dll!7c917e77() 	
 	ntdll.dll!7c917c0c() 	
 	ntdll.dll!7c917bf5() 	
 	ntdll.dll!7c917bb0() 	
 	msvcrt.dll!77c2c2e3() 	
 	msvcrt.dll!77c2c774() 	
 	libglib-2.0-0.dll!0047dd51() 	
 	libglib-2.0-0.dll!0047ddb1() 	
 	libglib-2.0-0.dll!004cb485() 	
 	libglib-2.0-0.dll!004ca5ce() 	
 	ntdll.dll!7c9101c7() 	
 	ntdll.dll!7c9102d2() 	
 	ntdll.dll!7c9102ed() 	
 	ntdll.dll!7c9105c8() 	
 	ntdll.dll!7c910551() 	
 	ntdll.dll!7c91056d() 	
 	kernel32.dll!7c81079e() 	
 	kernel32.dll!7c8107e1() 	
 	ntdll.dll!7c917bb0() 	
 	msvcrt.dll!77c2c756() 	
 	ntdll.dll!7c91056d() 	
 	msvcrt.dll!77c2c2de() 	
 	msvcrt.dll!77c2c2e3() 	
 	msvcrt.dll!77c2c774() 	
 	libglib-2.0-0.dll!0047dd51() 	
 	msvcrt.dll!77c2c2e3() 	
 	libglib-2.0-0.dll!0047ddb1() 	
 	libglib-2.0-0.dll!004cb485() 	
 	libglib-2.0-0.dll!004ca5ce() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c911538() 	
 	ntdll.dll!7c911596() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c9106ab() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c911538() 	
 	ntdll.dll!7c911596() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c9106ab() 	
 	ntdll.dll!7c910732() 	
 	ntdll.dll!7c9106ab() 	
 	ntdll.dll!7c9106eb() 	
 	ntdll.dll!7c910551() 	
 	ntdll.dll!7c91056d() 	
 	ntdll.dll!7c90e57c() 	
 	libglib-2.0-0.dll!004c39c1() 	
 	ntdll.dll!7c90e57c() 	
 	kernel32.dll!7c809c5a() 	
 	libglib-2.0-0.dll!004c39c1() 	
 	libglib-2.0-0.dll!004c4dda() 	
 	libglib-2.0-0.dll!0047304b() 	
 	msvcrt.dll!77c2c3c9() 	
 	ntdll.dll!7c9106eb() 	
 	msvcrt.dll!77c2c3c9() 	
 	msvcrt.dll!77c2c3ce() 	
 	msvcrt.dll!77c2c3e7() 	
 	msvcrt.dll!77c2c3ce() 	
 	winicon.exe!00402dde() 	
 	winicon.exe!0040472b() 	
 	libgimp-2.0-0.dll!0060238a() 	
 	msvcrt.dll!77c3a52e() 	
 	msvcrt.dll!77c34e29() 	
 	msvcrt.dll!77c34e42() 	
 	winicon.exe!004044a2() 	
 	winicon.exe!00404483() 	
 	msvcrt.dll!77c3aead() 	
 	winicon.exe!004011e7() 	
 	winicon.exe!00401258() 	
 	kernel32.dll!7c816d4f() 	
 	kernel32.dll!7c8399f3() 	


Other information: