Some better searching revealed this is a very old bug. From last
year:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&th=adfbc404c374e980&seekm=OF36816CDD.AE7D54AF-ONC1256B1F.005622DC%40icos.be&frame=off
I tried running GDB in GDB and I was able to get as far as seeing that
the floats seemed to be pushed onto the stack correctly until the
thread switch and all the ptrace stuff, but I wasn't totally sure if
the bug I was seeing at that point was in the GDB'd GDB or was the
same bug in the outter GDB.
[Mailing list changed to something with less spam :-)]