[ruby-dev:43062] sprintf("%f", 1e-7): Conditional jump or move depends on uninitialised value(s)

以下のように、sprintf("%f", 1e-7) に対し、valgrind が
  Conditional jump or move depends on uninitialised value(s)
と出力します。

% valgrind ./ruby -ve 'sprintf("%f", 1e-7)'
==21019== Memcheck, a memory error detector.
==21019== Copyright (C) 2002-2007, and GNU GPL'd, by Julian Seward et al.
==21019== Using LibVEX rev 1854, a library for dynamic binary translation.
==21019== Copyright (C) 2004-2007, and GNU GPL'd, by OpenWorks LLP.
==21019== Using valgrind-3.3.1-Debian, a dynamic binary
instrumentation framework.
==21019== Copyright (C) 2000-2007, and GNU GPL'd, by Julian Seward et al.
==21019== For more details, rerun with: -v
==21019==
ruby 1.9.3dev (2011-01-18 trunk 30590) [i686-linux]
==21019== Conditional jump or move depends on uninitialised value(s)
==21019==    at 0x80F5809: cvt (vsnprintf.c:1207)
==21019==    by 0x80F3CF7: BSD_vfprintf (vsnprintf.c:848)
==21019==    by 0x80F5AB0: ruby_snprintf (vsnprintf.c:1282)
==21019==    by 0x80F2FC9: rb_str_format (sprintf.c:1062)
==21019==    by 0x80EF60A: rb_f_sprintf (sprintf.c:437)
==21019==    by 0x814E29F: call_cfunc (vm_insnhelper.c:316)
==21019==    by 0x814E177: vm_call_cfunc (vm_insnhelper.c:403)
==21019==    by 0x814D736: vm_call_method (vm_insnhelper.c:525)
==21019==    by 0x81492AC: vm_exec_core (insns.def:1010)
==21019==    by 0x8156606: vm_exec (vm.c:1150)
==21019==    by 0x8156DDE: rb_iseq_eval_main (vm.c:1391)
==21019==    by 0x805C258: ruby_exec_internal (eval.c:225)
==21019==
==21019== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 34 from 1)
==21019== malloc/free: in use at exit: 196,977 bytes in 7,215 blocks.
==21019== malloc/free: 62,425 allocs, 55,210 frees, 8,538,279 bytes allocated.
==21019== For counts of detected errors, rerun with: -v
==21019== searching for pointers to 7,215 not-freed blocks.
==21019== checked 532,380 bytes.
==21019==
==21019== LEAK SUMMARY:
==21019==    definitely lost: 312 bytes in 6 blocks.
==21019==      possibly lost: 0 bytes in 0 blocks.
==21019==    still reachable: 196,665 bytes in 7,209 blocks.
==21019==         suppressed: 0 bytes in 0 blocks.
==21019== Rerun with --leak-check=full to see details of leaked memory.
-- 
[田中 哲][たなか あきら][Tanaka Akira]