1 files changed, 44 insertions, 0 deletions
diff --git a/recruiters/quizzes/end-quiz.txt b/recruiters/quizzes/end-quiz.txt
index 96bff5b..eedb3ba 100644
--- a/recruiters/quizzes/end-quiz.txt
+++ b/recruiters/quizzes/end-quiz.txt
@@ -171,3 +171,47 @@ docs: devmanual
 	package? Under which circumstances should you avoid this check and how?
 
 docs: devmanual
+
+21. When should USE flags be used? What are the cases where they should be
+    avoided? Consider the following examples. Explain what is wrong in them
+    and how would you improve them.
+
+docs: devmanual, common sense
+
+21.a. A large C++ application with long build time has:
+
+  # libcxx can be optionally used at run time via -stdlib=libc++
+  IUSE="libcxx"
+  DEPEND=""
+  RDEPEND="libcxx? ( dev-libs/libcxx )"
+
+21.b. A large package with long build time has:
+
+  inherit bash-completion-r1
+  IUSE="bash-completion"
+
+  src_install() {
+    default
+    use bash-completion && dobashcomp contrib/bash-completion/foo
+  }
+
+21.c. A package unconditionally installs 'foobar' executable which links
+      to libbar. The ebuild maintainer wanted to make it optional.
+      He used the following code:
+
+  IUSE="foobar"
+  RDEPEND="foobar? ( dev-libs/libbar )"
+  DEPEND="${RDEPEND}"
+
+  src_install() {
+    default
+    if ! use foobar; then
+      rm "${ED}"/usr/bin/foobar || die
+    fi
+  }
+
+21.d. A package has numerous configure switches which control a number
+      of optional features. All of them are enabled by default. They do
+      not have any external dependencies, and do not affect the package
+      size significantly. The ebuild author has added over 20 local USE
+      flags to control all of them.