cppcheck does not detect memset on struct with std container when size is multiplied

[Alexey Popov]

Example code:

struct A_TEST
{
   int m_nNumber;            
   char m_szID[5];
   std::vector<int> m_vStrings;
};

int main(int)
{
   std::vector<A_TEST> vec_A(5);
   memset(&vec_A[0], 0, sizeof(A_TEST) * vec_A.size());

   std::vector<A_TEST> vec_B(5);
   memset(&vec_B[0] , 0 , sizeof(A_TEST));
}

Cppcheck doesn't detect memset in line 11 - only in line 14:

cppcheck --enable=style --inconclusive --inline-suppr -j 4 --suppress=functionStatic --suppress=syntaxError --suppress=noExplicitConstructor --quiet . 2>&1
[main.cpp:14]: (error) Using 'memset' on struct that contains a 'std::vector'.

[raynebc]

One of the code validation programs I use complains if I declare variables after program code (ie. call to memset() ) in a code block. If you declare both vectors and then make both calls to memset() afteward, does Cppcheck still only warn about the second use of memset()?

[Alexey Popov]

It is not working either. Warns about the second use of memset only:

struct A_TEST
{
   int m_nNumber;
   char m_szID[5];
   std::vector<int> m_vStrings;
};

int main(int)
{
   std::vector<A_TEST> vec_A(5);
   std::vector<A_TEST> vec_B(5);

   memset(&vec_A[0], 0, sizeof(A_TEST) * vec_A.size());
   memset(&vec_B[0] , 0 , sizeof(A_TEST));
}

$ cppcheck --enable=style --inconclusive --inline-suppr -j 4 --suppress=functionStatic --suppress=syntaxError --suppress=noExplicitConstructor --quiet . 2>&1
[main.cpp:14]: (error) Using 'memset' on struct that contains a 'std::vector'.

[versat]

Thanks for the report, it really looks like a false negative to me.
I created ticket 8619 for this issue and modified/reduced the code a bit but it should still show exactly the issue you detected.

[Alexey Popov]

Thank you too.