This problem occurs quite often. Most recently, I attempted to install media-sound/lilypond. One of the dependencies is dev-scheme/guile. So when I run
# emerge -pv lilypond
[ebuild N ] dev-scheme/guile-1.8.2 USE="nls -debug -debug-freelist -debug-malloc -deprecated -discouraged -elisp -networking -regex -threads"
[ebuild N ] media-sound/lilypond-2.10.33 USE="emacs -debug -profile"
Portage proceeds to build guile, and then when it attempts to emerge lilypond, the following fatal error is produced:
"guile must be built with "depcrecated regex" use flags".
This might just be a problem with the lilypond ebuild, but this is far from the first time I've seen this. Portage should be able to figure out somehow that guile needs certain use flags and since it's already building it in the first place, it should build it right the first time. Or else if this feature already exists, more packages should take advantage of it.
Steps to Reproduce:
1. run "emerge -C guile lilypond" to remove said packages
2. ensure that "deprecated" and "regex" are not set as use flags in make.conf or package.use for dev-scheme/guile
3. emerge lilypond
Lilypond fails to emerge because guile was built with the wrong use flags. It was fixed by adding a new line to /etc/portage/package.use and rebuilding guile.
Portage should have built guile correctly the first time.
$ emerge --version
Portage 22.214.171.124 (default-linux/x86/2006.1, gcc-4.1.2, glibc-2.6.1-r0, 2.6.19-gentoo-r5 i686)
*** This bug has been marked as a duplicate of bug 2272 ***