Add KCONFIG_STRICT flag for flagging refs. to undefined syms

Settings KCONFIG_STRICT to y in the environment turns on warnings for
all references to undefined symbols within Kconfig files (with the only
gotcha that hex literals must be prefixed by 0x or 0X, to make it
possible to distinguish them from undefined references).

Always flagging undefined references gets awkward, as some projects
(e.g. the Linux kernel) use multiple Kconfig trees with shared files,
leading to some safe undefined references. It's helpful for other
projects though.

Having KCONFIG_STRICT as an environment variable is handy when multiple
tools are involved.

Piggyback a small README change re. warnings. Kconfiglib now has many
more warnings than the C tools.

1 files changed, 3 insertions, 7 deletions

diff --git a/README.rst b/README.rst
index eb9c77a..2af9e9f 100644
--- a/README.rst
+++ b/README.rst
@@ -272,14 +272,10 @@ Other features
   `multiprocessing <https://docs.python.org/3/library/multiprocessing.html>`_
   module. No global state is kept.
 
-- **Warning parity with the C implementation**
+- **Generates more warnings than the C implementation**
 
-  Generates the same warnings as the C implementation, plus a few extra ones.
-  Also detects dependency loops and ``source`` loops.
-
-  This is less important if the input is assumed to be well-formed, but makes
-  Kconfiglib a viable replacement for the C tools if e.g. a ``menuconfig``
-  interface is added.
+  Generates the same warnings as the C implementation, plus additional ones.
+  Also detects dependency and ``source`` loops.
 
   All warnings point out the location(s) in the ``Kconfig`` files where a
   symbol is defined, where applicable.