Issue #19469 has been updated by alanwu (Alan Wu). Could this be the cause of #19433? The stack traces seem to indicate generic IV table resizing. ---------------------------------------- Bug #19469: Crash when resizing generic iv list https://bugs.ruby-lang.org/issues/19469#change-102094 * Author: peterzhu2118 (Peter Zhu) * Status: Open * Priority: Normal * Backport: 2.7: DONTNEED, 3.0: DONTNEED, 3.1: DONTNEED, 3.2: REQUIRED ---------------------------------------- GitHub PR: https://github.com/ruby/ruby/pull/7407 The following script can sometimes trigger a crash: ```ruby GC.stress = true class Array def foo(bool) if bool @a = 1 @b = 2 @c = 1 else @c = 1 end end end obj = [] obj.foo(true) obj2 = [] obj2.foo(false) obj3 = [] obj3.foo(true) ``` This is because vm_setivar_default calls rb_ensure_generic_iv_list_size to resize the iv list. However, the call to gen_ivtbl_resize reallocs the iv list, and then inserts into the generic iv table. If the st_insert triggers a GC then the old iv list will be read during marking, causing a use-after-free bug. -- https://bugs.ruby-lang.org/