Using uninitialized memory 'buf' in line 11173 v2.1.1?

[mireiner]

json.hpp v2.1.1

Using uninitialized memory 'buf'?

Lines

11149 std::array<char, 64> buf;

---

11173 if ((len + 1) < buf.size())
11174 {
11175 std::copy(m_start, m_end, buf.begin());
11176 buf[len] = 0;
11177 buf[ds_pos] = decimal_point_char;
11178 data = buf.data();
11179 }

[nlohmann]

No, this is fine. We checked the code with Valgrind and clang's sanitizers.

Wenn you look at https://github.com/nlohmann/json/blob/v2.1.1/src/json.hpp#L11153 you see that

• len = m_end - m_start
• len > 0
• (len + 1) < buf.size()
• std::copy(m_start, m_end, buf.begin()) copies len bytes to buf
• buf[len] = 0 terminates buf
• buf[ds_pos] = decimal_point_char replaces the decimal point
• data = buf.data() reads buf
• buf is not read at any other location

[mireiner]

Visual Studio 2017 Code Analyser shows C6001 warning message at line 11173:
"json.hpp(11173): warning C6001: Using uninitialized memory 'buf'."

Warning C6001 means:
https://msdn.microsoft.com/en-us/library/3fb5eatz.aspx

'buf' isn't initialized at line 11173. So I wondered what the if statement will check in line 11173, because 'buf.size()' will most likely be always 0 at that point. Isn't it?

[nlohmann]

std::array::size() returns the size of the array (i.e., the template parameter) which is 64 in this case. It seems as if the warning is a false positive.

[mireiner]

Sorry for the false report. Feel free to delete this entry.

[nlohmann]

No problem! Thanks for reporting!