>I have procedure A.
>
>This procedure calls procedure B, that I have changed with "alter
>procedure".

>If I try to delete procedure A, I get the message

Hi!
You need to compile again procedure A too. When A includes B then change
in B is not reflected in A (that A still contains copy of old B
procedure).

It seems that Firebird does not call B from A, but that A contains
expanded code from B (somehting like macro expansion), but it is pure
guess...