Provide as much diagnostic information as possible in "panic: ..." messages.

The convention is that when the interpreter dies with an internal error, the
message starts "panic: ". Historically, many panic messages had been terse
fixed strings, which means that the out-of-range values that triggered the
panic are lost. Now we try to report these values, as such panics may not be
repeatable, and the original error message may be the only diagnostic we get
when we try to find the cause.

We can't report diagnostics when the panic message is generated by something
other than croak(), as we don't have *printf-style format strings. Don't
attempt to report values in panics related to *printf buffer overflows, as
attempting to format the values to strings may repeat or compound the
original error.

1 files changed, 6 insertions, 4 deletions

diff --git a/op.c b/op.c
index d4dcf53272..12f0cbc951 100644
--- a/op.c
+++ b/op.c
@@ -837,7 +837,8 @@ Perl_op_contextualize(pTHX_ OP *o, I32 context)
 	case G_ARRAY:  return list(o);
 	case G_VOID:   return scalarvoid(o);
 	default:
-	    Perl_croak(aTHX_ "panic: op_contextualize bad context");
+	    Perl_croak(aTHX_ "panic: op_contextualize bad context %ld",
+		       (long) context);
 	    return o;
     }
 }
@@ -8149,7 +8150,7 @@ Perl_ck_grep(pTHX_ OP *o)
 	return o;
     kid = cLISTOPo->op_first->op_sibling;
     if (kid->op_type != OP_NULL)
-	Perl_croak(aTHX_ "panic: ck_grep");
+	Perl_croak(aTHX_ "panic: ck_grep, type=%u", (unsigned) kid->op_type);
     kid = kUNOP->op_first;
 
     if (!gwop)
@@ -8857,7 +8858,7 @@ Perl_ck_split(pTHX_ OP *o)
 
     kid = cLISTOPo->op_first;
     if (kid->op_type != OP_NULL)
-	Perl_croak(aTHX_ "panic: ck_split");
+	Perl_croak(aTHX_ "panic: ck_split, type=%u", (unsigned) kid->op_type);
     kid = kid->op_sibling;
     op_free(cLISTOPo->op_first);
     if (kid)
@@ -9081,7 +9082,8 @@ Perl_ck_entersub_args_proto(pTHX_ OP *entersubop, GV *namegv, SV *protosv)
     const char *e = NULL;
     PERL_ARGS_ASSERT_CK_ENTERSUB_ARGS_PROTO;
     if (SvTYPE(protosv) == SVt_PVCV ? !SvPOK(protosv) : !SvOK(protosv))
-	Perl_croak(aTHX_ "panic: ck_entersub_args_proto CV with no proto");
+	Perl_croak(aTHX_ "panic: ck_entersub_args_proto CV with no proto,"
+		   "flags=%lx", (unsigned long) SvFLAGS(protosv));
     if (SvTYPE(protosv) == SVt_PVCV)
 	 proto = CvPROTO(protosv), proto_len = CvPROTOLEN(protosv);
     else proto = SvPV(protosv, proto_len);