From 1ea7da67c3186119551ff88c5c6b05de05393ce0 Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Sat, 23 Mar 2024 02:35:32 +0100
Subject: make: config based example

---
 src/development/make.md | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/src/development/make.md b/src/development/make.md
index 254a7d7..fdef47e 100644
--- a/src/development/make.md
+++ b/src/development/make.md
@@ -137,5 +137,40 @@ Resolve each file name as canonical path.
 $(realpath fname1 fname2 ..)
 ```
 
+## Examples
+
+### Config based settings
+```make
+conf-y      := default
+conf-$(FOO) := $(conf-y) foo
+conf-$(BAR) := $(conf-y) bar
+
+libs-y      := libdef
+libs-$(FOO) += libfoo
+libs-$(BAR) += libbar
+
+all:
+	@echo "conf-y: $(conf-y)"
+	@echo "libs-y: $(libs-y)"
+```
+Yields the following results.
+```sh
+$ make
+conf-y: default
+libs-y: libdef
+
+$ make FOO=y
+conf-y: default foo
+libs-y: libdef libfoo
+
+$ make BAR=y
+conf-y: default bar
+libs-y: libdef libbar
+
+$ make FOO=y BAR=y
+conf-y: default foo bar
+libs-y: libdef libfoo libbar
+```
+
 [make-var-override]: https://www.gnu.org/software/make/manual/html_node/Overriding.html
 [make-patsubst]: https://www.gnu.org/software/make/manual/html_node/Text-Functions.html#index-patsubst-1
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