docs: Calling gmodule funcs in constructors may deadlock

Fixes #1443.

docs/reference/gmodule/modules.md

@@ -7,6 +7,9 @@ These functions provide a portable way to dynamically load object files
 systems that provide an implementation of `dlopen()` (e.g. Linux/Sun), as
 well as Windows platforms via DLLs.
 
+Do not call these functions from within global constructors (for example, those
+using GCC’s `__attribute__((constructor))` attribute) as this may lead to deadlock.
+
 A program which wants to use these functions must be linked to the libraries
 output by the command:
 

gmodule/gmodule.c

@@ -59,6 +59,10 @@
  * The #GModule struct is an opaque data structure to represent a
  * [dynamically-loaded module](modules.html#dynamic-loading-of-modules).
  * It should only be accessed via the following functions.
+ * 
+ * To ensure correct lock ordering, these functions must not be called from
+ * global constructors (for example, those using GCC’s
+ * `__attribute__((constructor))` attribute).
  */
 
 /**