While building glibc cc1 grows to more then 3Gb, sucking up all available memory. This happens while compiling sysdeps/ieee754/dbl-64/dosincos.c.
Yes, this has been already reported (and it is many times more than 3GB).
As a temporary workaround, build this file with -fno-var-tracking-assignments,
I hope when Alex will return from this week's travelling he'll work on it.
Should be fixed in gcc-4.4.2-4.fc12 (though, this is not tagged into dist-f12 yet).