doc: Add warning about --force-fallback-for [skip ci]
@@ -236,6 +236,28 @@ the following command-line options:
but you only want to build against the library sources for a few
of them.
+ **Warning**: This could lead to mixing system and subproject version of the
+ same library in the same process. Take this case as example:
+ - Libraries `glib-2.0` and `gstreamer-1.0` are installed on your system.
+ - `gstreamer-1.0` depends on `glib-2.0`, pkg-config file `gstreamer-1.0.pc`
+ has `Requires: glib-2.0`.
+ - In your application build definition you do:
+ ```meson
+ executable('app', ...,
+ dependencies: [
+ dependency('glib-2.0', fallback: 'glib'),
+ dependency('gstreamer-1.0', fallback: 'gstreamer')],
+ )
+ ```
+ - You configure with `--force-fallback-for=glib`.
+ This result in linking to two different versions of library `glib-2.0`
+ because `dependency('glib-2.0', fallback: 'glib')` will return the
+ subproject dependency, but `dependency('gstreamer-1.0', fallback: 'gstreamer')`
+ will not fallback and return the system dependency, including `glib-2.0`
+ library. To avoid that situation, every dependency that itself depend on
+ `glib-2.0` must also be forced to fallback, in this case with
+ `--force-fallback-for=glib,gsteamer`.
+
## Download subprojects
*Since 0.49.0*
