Guard callinfo

Callinfo was being written in to an array and the GC would not see the
reference on the stack.  `new_insn_send` creates a new callinfo object,
then it calls `new_insn_core`.  `new_insn_core` allocates a new INSN
linked list item, which can end up calling `xmalloc` which will trigger
a GC:

  https://github.com/ruby/ruby/blob/70cd351c7c71c48ee18d7c01e851a89614086f8f/compile.c#L968-L969

Since the callinfo object isn't on the stack, the GC won't see it, and
it can get collected.  This patch just refactors `new_insn_send` to keep
the object on the stack

Co-authored-by: John Hawthorn <john@hawthorn.email>

1 files changed, 5 insertions, 2 deletions

diff --git a/compile.c b/compile.c
index d1586acf31..388d476c68 100644
--- a/compile.c
+++ b/compile.c
@@ -1302,12 +1302,15 @@ static INSN *
 new_insn_send(rb_iseq_t *iseq, int line_no, ID id, VALUE argc, const rb_iseq_t *blockiseq, VALUE flag, struct rb_callinfo_kwarg *keywords)
 {
     VALUE *operands = compile_data_calloc2(iseq, sizeof(VALUE), 2);
-    operands[0] = (VALUE)new_callinfo(iseq, id, FIX2INT(argc), FIX2INT(flag), keywords, blockiseq != NULL);
+    VALUE ci = (VALUE)new_callinfo(iseq, id, FIX2INT(argc), FIX2INT(flag), keywords, blockiseq != NULL);
+    operands[0] = ci;
     operands[1] = (VALUE)blockiseq;
     if (blockiseq) {
         RB_OBJ_WRITTEN(iseq, Qundef, blockiseq);
     }
-    return new_insn_core(iseq, line_no, BIN(send), 2, operands);
+    INSN *insn = new_insn_core(iseq, line_no, BIN(send), 2, operands);
+    RB_GC_GUARD(ci);
+    return insn;
 }
 
 static rb_iseq_t *