fix(blob): allow blob object to be initialized with null-pointer ch…

…ar array whose length must be zero (#2110)

Fix #2109.

Null-pointer char array with zero length is allowed to be used to initialize
`blob` object. Use `DCHECK` instead to check if the pointer is valid while
initializing `blob` object.

src/utils/blob.h

@@ -109,7 +109,9 @@ class blob
     /// NOTE: this operation is not efficient since it involves a memory copy.
     [[nodiscard]] static blob create_from_bytes(const char *s, size_t len)
     {
-        CHECK_NOTNULL(s, "null source pointer would lead to undefined behaviour");
+        DCHECK(s != nullptr || len == 0,
+               "null source pointer with non-zero length would lead to "
+               "undefined behaviour");
 
         std::shared_ptr<char> s_arr(new char[len], std::default_delete<char[]>());
         memcpy(s_arr.get(), s, len);

src/utils/test/blob_test.cpp

@@ -24,6 +24,25 @@
 
 namespace dsn {
 
+TEST(BlobTest, CreateFromZeroLengthNullptr)
+{
+    const auto &obj = blob::create_from_bytes(nullptr, 0);
+
+    EXPECT_EQ(0, obj.length());
+    EXPECT_EQ(0, obj.size());
+}
+
+#ifndef NDEBUG
+
+TEST(BlobTest, CreateFromNonZeroLengthNullptr)
+{
+    ASSERT_DEATH({ const auto &obj = blob::create_from_bytes(nullptr, 1); },
+                 "null source pointer with non-zero length would lead to "
+                 "undefined behaviour");
+}
+
+#endif
+
 struct blob_base_case
 {
     std::string expected_str;
@@ -32,7 +51,7 @@ struct blob_base_case
 class BlobBaseTest : public testing::TestWithParam<blob_base_case>
 {
 public:
-    void SetUp() override
+    BlobBaseTest()
     {
         const auto &test_case = GetParam();
         _expected_str = test_case.expected_str;