Issue #20455 has been updated by Eregon (Benoit Daloze). @ko1 (and the code) pointed me to `$!` is `rb_ec_get_errinfo`, which walks the stack to find the first `rescue`/`ensure` (does it stop at the first ensure if it's an ensure without an active exception?) and uses `ec->errinfo` if not, while `rb_errinfo` is just `GET_EC()->errinfo`. I'm not sure what this means in terms of semantics, that they are the same but only if no rescue/ensure on the stack, and otherwise they are fully separate? It sounds like very odd semantics. BTW the header docs at https://github.com/ruby/ruby/blob/6f4f360fc46269eaba753cafe557519677a45a11/… seems not quite true and rather misleading. ---------------------------------------- Bug #20455: rb_errinfo() inconsistent with $! in the caller Ruby code https://bugs.ruby-lang.org/issues/20455#change-108121 * Author: Eregon (Benoit Daloze) * Status: Open * ruby -v: ruby 3.4.0dev (2024-04-25T08:12:47Z master 64bd8e41df) [x86_64-linux] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- This (slightly modified for clarity) test in ruby/spec demonstrates the unexpected result: ```ruby describe "rb_errinfo" do def err $! end it "is cleared when entering a C method" do begin raise StandardError rescue $!.class.should == StandardError err.class.should == StandardError @s.rb_errinfo().should == nil end end ``` Why does `rb_errinfo()` return nil there, when $! is set in the caller (and $! isn't per frame but per thread, as shown with `err`)? Is this bug? If not, what is the logic and reason for clearing `$!` when calling a method defined in C? -- https://bugs.ruby-lang.org/