Change validation messages for unknown memory

Use validation error message "invalid memory index N" for both N != 0
and data segments without any memory in the module. Inspired by messages
in wasm reference interpreter.

Author: chfast

lib/fizzy/parser.cpp

@@ -410,8 +410,14 @@ inline parser_result<Data> parse(const uint8_t* pos, const uint8_t* end)
 {
     MemIdx memory_index;
     std::tie(memory_index, pos) = leb128u_decode<uint32_t>(pos, end);
+
+    // TODO: The check should be memory_index < num_of_memories (0 or 1),
+    //       but access to the memory section of the module is needed.
     if (memory_index != 0)
-        throw validation_error{"unexpected memidx value " + std::to_string(memory_index)};
+    {
+        throw validation_error{
+            "invalid memory index " + std::to_string(memory_index) + " (only memory 0 is allowed)"};
+    }
 
     ConstantExpression offset;
     // Offset expression is required to have i32 result value
@@ -560,7 +566,10 @@ std::unique_ptr<const Module> parse(bytes_view input)
     }
 
     if (!module->datasec.empty() && !module->has_memory())
-        throw validation_error{"data section encountered without a memory section"};
+    {
+        throw validation_error{
+            "invalid memory index 0 (data section encountered without a memory section)"};
+    }
 
     for (const auto& data : module->datasec)
     {

test/unittests/parser_test.cpp

@@ -1324,7 +1324,8 @@ TEST(parser, data_section_memidx_nonzero)
 {
     const auto section_contents = make_vec({"0141010b0100"_bytes});
     const auto bin = bytes{wasm_prefix} + make_section(11, section_contents);
-    EXPECT_THROW_MESSAGE(parse(bin), parser_error, "unexpected memidx value 1");
+    EXPECT_THROW_MESSAGE(
+        parse(bin), validation_error, "invalid memory index 1 (only memory 0 is allowed)");
 }
 
 TEST(parser, data_section_invalid_initializer)
@@ -1338,15 +1339,15 @@ TEST(parser, data_section_invalid_initializer)
 TEST(parser, data_section_empty_vector_without_memory)
 {
     const auto bin = bytes{wasm_prefix} + make_section(11, make_vec({"0041010b00"_bytes}));
-    EXPECT_THROW_MESSAGE(
-        parse(bin), validation_error, "data section encountered without a memory section");
+    EXPECT_THROW_MESSAGE(parse(bin), validation_error,
+        "invalid memory index 0 (data section encountered without a memory section)");
 }
 
 TEST(parser, data_section_without_memory)
 {
     const auto bin = bytes{wasm_prefix} + make_section(11, make_vec({"0041010b02aaff"_bytes}));
-    EXPECT_THROW_MESSAGE(
-        parse(bin), validation_error, "data section encountered without a memory section");
+    EXPECT_THROW_MESSAGE(parse(bin), validation_error,
+        "invalid memory index 0 (data section encountered without a memory section)");
 }
 
 TEST(parser, data_section_out_of_bounds)