fix uninitialized memory access in WasmModule

Without this, the cached module vectors have garbage values, which are
passed to realloc(). For some reason this doesn't blow up ASAN or MSAN.

This change fixes #10. Thanks to @mbodart for the fix!

2 files changed, 33 insertions, 31 deletions

diff --git a/src/wasm-parser.c b/src/wasm-parser.c
index d5bbe1a0..940c3619 100644
--- a/src/wasm-parser.c
+++ b/src/wasm-parser.c
@@ -601,8 +601,8 @@ static const yytype_uint16 yyrline[] =
     1021,  1028,  1034,  1039,  1045,  1052,  1058,  1063,  1069,  1076,
     1082,  1093,  1094,  1101,  1111,  1122,  1126,  1133,  1137,  1144,
     1152,  1159,  1170,  1177,  1181,  1193,  1194,  1202,  1210,  1218,
-    1226,  1234,  1242,  1252,  1329,  1330,  1336,  1341,  1348,  1354,
-    1363,  1364,  1371,  1380,  1381,  1384,  1385,  1392,  1398
+    1226,  1234,  1242,  1252,  1330,  1331,  1337,  1342,  1349,  1355,
+    1364,  1365,  1372,  1381,  1382,  1385,  1386,  1393,  1399
 };
 #endif
 
@@ -3835,6 +3835,7 @@ yyreduce:
   case 173:
 #line 1252 "src/wasm-parser.y" /* yacc.c:1646  */
     {
+      ZEROMEM((yyval.module));
       (yyval.module).loc = (yylsp[-2]);
       (yyval.module).fields = (yyvsp[-1].module_fields);
 
@@ -3905,38 +3906,38 @@ yyreduce:
         }
       }
     }
-#line 3909 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3910 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 174:
-#line 1329 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1330 "src/wasm-parser.y" /* yacc.c:1646  */
     { (yyval.command).type = WASM_COMMAND_TYPE_MODULE; (yyval.command).module = (yyvsp[0].module); }
-#line 3915 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3916 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 175:
-#line 1330 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1331 "src/wasm-parser.y" /* yacc.c:1646  */
     {
       (yyval.command).type = WASM_COMMAND_TYPE_INVOKE;
       (yyval.command).invoke.loc = (yylsp[-3]);
       (yyval.command).invoke.name = (yyvsp[-2].text);
       (yyval.command).invoke.args = (yyvsp[-1].consts);
     }
-#line 3926 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3927 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 176:
-#line 1336 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1337 "src/wasm-parser.y" /* yacc.c:1646  */
     {
       (yyval.command).type = WASM_COMMAND_TYPE_ASSERT_INVALID;
       (yyval.command).assert_invalid.module = (yyvsp[-2].module);
       (yyval.command).assert_invalid.text = (yyvsp[-1].text);
     }
-#line 3936 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3937 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 177:
-#line 1341 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1342 "src/wasm-parser.y" /* yacc.c:1646  */
     {
       (yyval.command).type = WASM_COMMAND_TYPE_ASSERT_RETURN;
       (yyval.command).assert_return.invoke.loc = (yylsp[-5]);
@@ -3944,22 +3945,22 @@ yyreduce:
       (yyval.command).assert_return.invoke.args = (yyvsp[-3].consts);
       (yyval.command).assert_return.expected = (yyvsp[-1].const_);
     }
-#line 3948 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3949 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 178:
-#line 1348 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1349 "src/wasm-parser.y" /* yacc.c:1646  */
     {
       (yyval.command).type = WASM_COMMAND_TYPE_ASSERT_RETURN_NAN;
       (yyval.command).assert_return_nan.invoke.loc = (yylsp[-4]);
       (yyval.command).assert_return_nan.invoke.name = (yyvsp[-3].text);
       (yyval.command).assert_return_nan.invoke.args = (yyvsp[-2].consts);
     }
-#line 3959 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3960 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 179:
-#line 1354 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1355 "src/wasm-parser.y" /* yacc.c:1646  */
     {
       (yyval.command).type = WASM_COMMAND_TYPE_ASSERT_TRAP;
       (yyval.command).assert_trap.invoke.loc = (yylsp[-5]);
@@ -3967,26 +3968,26 @@ yyreduce:
       (yyval.command).assert_trap.invoke.args = (yyvsp[-3].consts);
       (yyval.command).assert_trap.text = (yyvsp[-1].text);
     }
-#line 3971 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3972 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 180:
-#line 1363 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1364 "src/wasm-parser.y" /* yacc.c:1646  */
     { ZEROMEM((yyval.commands)); }
-#line 3977 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3978 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 181:
-#line 1364 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1365 "src/wasm-parser.y" /* yacc.c:1646  */
     {
       (yyval.commands) = (yyvsp[-1].commands);
       CHECK_ALLOC(wasm_append_command_value(&(yyval.commands), &(yyvsp[0].command)));
     }
-#line 3986 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3987 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 182:
-#line 1371 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1372 "src/wasm-parser.y" /* yacc.c:1646  */
     {
       (yyval.const_).loc = (yylsp[-2]);
       if (!read_const((yyvsp[-2].type), (yyvsp[-1].text).start, (yyvsp[-1].text).start + (yyvsp[-1].text).length, &(yyval.const_)))
@@ -3994,38 +3995,38 @@ yyreduce:
                    (yyvsp[-1].text).start);
       free((char*)(yyvsp[-1].text).start);
     }
-#line 3998 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 3999 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 183:
-#line 1380 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1381 "src/wasm-parser.y" /* yacc.c:1646  */
     { (yyval.const_).type = WASM_TYPE_VOID; }
-#line 4004 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 4005 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 185:
-#line 1384 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1385 "src/wasm-parser.y" /* yacc.c:1646  */
     { ZEROMEM((yyval.consts)); }
-#line 4010 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 4011 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 186:
-#line 1385 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1386 "src/wasm-parser.y" /* yacc.c:1646  */
     {
       (yyval.consts) = (yyvsp[-1].consts);
       CHECK_ALLOC(wasm_append_const_value(&(yyval.consts), &(yyvsp[0].const_)));
     }
-#line 4019 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 4020 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
   case 187:
-#line 1392 "src/wasm-parser.y" /* yacc.c:1646  */
+#line 1393 "src/wasm-parser.y" /* yacc.c:1646  */
     { (yyval.script).commands = (yyvsp[0].commands); parser->script = (yyval.script); }
-#line 4025 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 4026 "src/wasm-parser.c" /* yacc.c:1646  */
     break;
 
 
-#line 4029 "src/wasm-parser.c" /* yacc.c:1646  */
+#line 4030 "src/wasm-parser.c" /* yacc.c:1646  */
       default: break;
     }
   /* User semantic actions sometimes alter yychar, and that requires
@@ -4260,7 +4261,7 @@ yyreturn:
 #endif
   return yyresult;
 }
-#line 1401 "src/wasm-parser.y" /* yacc.c:1906  */
+#line 1402 "src/wasm-parser.y" /* yacc.c:1906  */
 
 
 void wasm_error(WasmLocation* loc,
diff --git a/src/wasm-parser.y b/src/wasm-parser.y
index 0e3a8dcd..56940f6e 100644
--- a/src/wasm-parser.y
+++ b/src/wasm-parser.y
@@ -1250,6 +1250,7 @@ module_fields :
 ;
 module :
     LPAR MODULE module_fields RPAR {
+      ZEROMEM($$);
       $$.loc = @2;
       $$.fields = $3;