From: leonerd-cpan [...] leonerd.org.uk

https://rt.cpan.org/Public/Bug/Display.html?id=137952

--- old/src/class.c	2021-07-30 17:08:56 +0000
+++ new/src/class.c	2021-07-31 12:55:46 +0000
@@ -87,6 +87,9 @@
 #define embed_cv(cv, embedding)  S_embed_cv(aTHX_ cv, embedding)
 static CV *S_embed_cv(pTHX_ CV *cv, RoleEmbedding *embedding)
 {
+  assert(cv);
+  assert(CvOUTSIDE(cv));
+
   CV *embedded_cv = cv_clone(cv);
   SV *embeddingsv = embedding->embeddingsv;
 
@@ -358,6 +361,19 @@
 
   ENTER;
 
+  if(!PL_compcv) {
+    /* We require the initslots CV to have a CvOUTSIDE, or else cv_clone()
+     * will segv when we compose role slots. Any class dynamically generated
+     * by string eval() will likely not get one, because it won't inherit a
+     * PL_compcv here. We'll fake it up
+     *   See also  https://rt.cpan.org/Ticket/Display.html?id=137952
+     */
+    SAVEVPTR(PL_compcv);
+    PL_compcv = find_runcv(0);
+
+    assert(PL_compcv);
+  }
+
   I32 floor_ix = start_subparse(FALSE, 0);
   SAVEFREESV(PL_compcv);
 
@@ -519,6 +535,9 @@
 
   meta->initslots = newATTRSUB(floor_ix, NULL, NULL, NULL, ops);
 
+  assert(meta->initslots);
+  assert(CvOUTSIDE(meta->initslots));
+
   LEAVE;
 }