When invoked with --db-attach=yes, the symbol reader spews 563 lines of:
   DWARF2 CFI reader: unhandled CFI instruction 0:18
for libc.  The compiler is gcc-4.1.0-2.  [Built from VALGRIND_3_1_BRANCH about
2006-03-07 0400 UTC; run on amd64 Fedora Core 5, glibc-2.4-1]

The -v verbose output from memcheck begins:
--5832--   
/home/jreiser/rpmbuild/BUILD/glibc-20060306T1239/build-x86_64-linuxnptl/csu/tst-atomic
--5832-- Startup, with flags:
--5832--    -v
--5832--    --db-attach=yes
--5832-- Contents of /proc/version:
--5832--   Linux version 2.6.15-1.2009.4.2_FC5
(bhcompile@hs20-bc2-3.build.redhat.com) (gcc version 4.1.0 20060228 (Red Hat
4.1.0-1)) #1 SMP Thu Mar 2 18:10:22 EST 2006
--5832-- Arch and subarch: AMD64, NONE
--5832-- Valgrind library directory: /usr/local/valgrind-branch31/lib/valgrind
--5832-- Reading syms from
/home/jreiser/rpmbuild/BUILD/glibc-20060306T1239/build-x86_64-linuxnptl/elf/ld.so
(0x0)
--5832-- Reading syms from
/usr/local/valgrind-branch31/lib/valgrind/amd64-linux/memcheck (0x70000000)
--5832--    object doesn't have a dynamic symbol table
--5832-- Reading suppressions file:
/usr/local/valgrind-branch31/lib/valgrind/default.supp
--5832-- Reading syms from
/home/jreiser/rpmbuild/BUILD/glibc-20060306T1239/build-x86_64-linuxnptl/csu/tst-atomic
(0x400000)
--5832-- Reading syms from
/usr/local/valgrind-branch31/lib/valgrind/amd64-linux/vgpreload_core.so (0x4802000)
--5832-- Reading syms from
/usr/local/valgrind-branch31/lib/valgrind/amd64-linux/vgpreload_memcheck.so
(0x4903000)
--5832-- REDIR: 0x13A00 (index) redirected to 0x49063A0 (index)
--5832-- REDIR: 0x13BB0 (strcmp) redirected to 0x4906510 (strcmp)
--5832-- REDIR: 0x13BE0 (strlen) redirected to 0x4906440 (strlen)
--5832-- Reading syms from
/home/jreiser/rpmbuild/BUILD/glibc-20060306T1239/build-x86_64-linuxnptl/libc.so
(0x4A0A000)
--5832-- DWARF2 CFI reader: unhandled CFI instruction 0:18
--5832-- DWARF2 CFI reader: unhandled CFI instruction 0:18
   [561 more copies of line above]