From 8780bc0b8ebd3492c58f1ce221e0d87de170c6ac Mon Sep 17 00:00:00 2001
From: Nicolas Williams <nico@cryptonector.com>
Date: Mon, 7 Jul 2014 16:03:32 -0500
Subject: [PATCH] Better check for lib has only functions (fix #138)

---
 compile.c     | 10 ++++++++++
 compile.h     |  2 ++
 execute.c     |  2 ++
 opcode_list.h |  2 ++
 parser.y      | 10 +++++++---
 5 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/compile.c b/compile.c
index 2a1b8b89..b3e58041 100644
--- a/compile.c
+++ b/compile.c
@@ -441,6 +441,16 @@ block gen_definedor(block a, block b) {
                tail);
 }
 
+int block_has_main(block top) {
+  return top.first && top.first->op == TOP;
+}
+
+int block_is_funcdef(block b) {
+  if (b.first != NULL && b.first->op == CLOSURE_CREATE)
+    return 1;
+  return 0;
+}
+
 block gen_condbranch(block iftrue, block iffalse) {
   iftrue = BLOCK(iftrue, gen_op_target(JUMP, iffalse));
   return BLOCK(gen_op_target(JUMP_F, iftrue), iftrue, iffalse);
diff --git a/compile.h b/compile.h
index 0640a961..9ad732a2 100644
--- a/compile.h
+++ b/compile.h
@@ -48,6 +48,8 @@ block gen_cbinding(const struct cfunction* functions, int nfunctions, block b);
 void block_append(block* b, block b2);
 block block_join(block a, block b);
 int block_has_only_binders(block, int bindflags);
+int block_has_main(block);
+int block_is_funcdef(block b);
 block block_bind(block binder, block body, int bindflags);
 block block_bind_referenced(block binder, block body, int bindflags);
 
diff --git a/execute.c b/execute.c
index f384420e..7b8f8f8e 100644
--- a/execute.c
+++ b/execute.c
@@ -315,6 +315,8 @@ jv jq_next(jq_state *jq) {
     switch (opcode) {
     default: assert(0 && "invalid instruction");
 
+    case TOP: break;
+
     case LOADK: {
       jv v = jv_array_get(jv_copy(frame_current(jq)->bc->constants), *pc++);
       assert(jv_is_valid(v));
diff --git a/opcode_list.h b/opcode_list.h
index b3b0f2e5..284c3686 100644
--- a/opcode_list.h
+++ b/opcode_list.h
@@ -34,3 +34,5 @@ OP(CLOSURE_PARAM, DEFINITION, 0, 0)
 OP(CLOSURE_REF, CLOSURE_REF_IMM, 0, 0)
 OP(CLOSURE_CREATE, DEFINITION, 0, 0)
 OP(CLOSURE_CREATE_C, DEFINITION, 0, 0)
+
+OP(TOP, NONE, 0, 0)
diff --git a/parser.y b/parser.y
index 7c53d285..6abcb473 100644
--- a/parser.y
+++ b/parser.y
@@ -206,7 +206,7 @@ static block gen_update(block object, block val, int optype) {
 %%
 TopLevel:
 Exp {
-  *answer = $1;
+  *answer = BLOCK(gen_op_simple(TOP), $1);
 } |
 FuncDefs {
   *answer = $1;
@@ -222,7 +222,10 @@ FuncDef FuncDefs {
 
 Exp:
 FuncDef Exp %prec ';' {
-  $$ = block_bind($1, $2, OP_IS_CALL_PSEUDO);
+  if (block_is_funcdef($2))
+    $$ = block_bind($1, $2, OP_IS_CALL_PSEUDO);
+  else
+    $$ = block_bind($1, BLOCK(gen_op_simple(TOP), $2), OP_IS_CALL_PSEUDO);
 } |
 
 Term "as" '$' IDENT '|' Exp {
@@ -682,9 +685,10 @@ int jq_parse(struct locfile* locations, block* answer) {
 int jq_parse_library(struct locfile* locations, block* answer) {
   int errs = jq_parse(locations, answer);
   if (errs) return errs;
-  if (!block_has_only_binders(*answer, OP_IS_CALL_PSEUDO)) {
+  if (block_has_main(*answer)) {
     locfile_locate(locations, UNKNOWN_LOCATION, "error: library should only have function definitions, not a main expression");
     return 1;
   }
+  assert(block_has_only_binders(*answer, OP_IS_CALL_PSEUDO));
   return 0;
 }