During the implementation of WT-12422 we've made a change to F_ISSET which has the downstream effect of making clang's type checking stricter. The code is functionally identical, but s_clang_scan now reports an Array subscript is undefined [core.uninitialized.ArraySubscript]warning inside the {}wt_verbose_level_multi _and }}{{_wt_verbose_multi macros.

Tracing this back the warning comes from using multi_category.categories[__v_idx], where multicategory has been created by a call to the WT_VERB_RECOVERY_RTS macro.
WT_VERB_RECOVERY_RTS returns one of two structs that are defined at compile time, so it can't return NULL. I think this is due to initialising the WT_VERBOSE_MULTI_CATEGORY->categories field which is of type (WT_VERBOSE_CATEGORY *) with an array {}.

This ticket can be timeboxed and the the scope is investigating a fix. If none can be found then this ticket can be closed and we'll keep the suppressions in s_clang_scan.diff

To reproduce - once WT-12422 is merged into develop - delete this line

wiredtiger/src/rollback_to_stable/rts_btree.c Array subscript is undefined [core.uninitialized.ArraySubscript]

from dist/s_clang_scan.diff and run s_clang_scan.
Note that s_clang_scan will also fail when expected errors in s_clang_scan.diff are missing from the clang_scan output, so if you see lines in the diff that start with a < like

< wiredtiger/src/rollback_to_stable/rts_btree.c Array subscript is undefined [core.uninitialized.ArraySubscript] 

they just need to be deleted from s_clang_scan.diff