+ /* If NULL, this is an ordinary partial symbol table.
+
+ If non-NULL, this holds a single includer of this partial symbol
+ table, and this partial symbol table is a shared one.
+
+ A shared psymtab is one that is referenced by multiple other
+ psymtabs, and which conceptually has its contents directly
+ included in those.
+
+ Shared psymtabs have special semantics. When a search finds a
+ symbol in a shared table, we instead return one of the non-shared
+ tables that include this one.
+
+ A shared psymtabs can be referred to by other shared ones.
+
+ The psymtabs that refer to a shared psymtab will list the shared
+ psymtab in their 'dependencies' array.
+
+ In DWARF terms, a shared psymtab is a DW_TAG_partial_unit; but
+ of course using a name based on that would be too confusing, so
+ "shared" was chosen instead.
+
+ Only a single user is needed because, when expanding a shared
+ psymtab, we only need to expand its "canonical" non-shared user.
+ The choice of which one should be canonical is left to the
+ debuginfo reader; it can be arbitrary. */
+
+ struct partial_symtab *user;
+