CPP

error: ‘memset’ was not declared in this scope in cpp

C: #include <string.h>

C++: #include <cstring>

NOTE: inclusion of above headers works fine 

Compiler error: memset was not declared in this scope

// na verdade só precisa incluir a proxima linha:
#include <cstring>
// isso já resolve o problema, o resto abaixo é só info adicional

$ man memset

MEMSET(3)                BSD Library Functions Manual                MEMSET(3)

NAME
     memset -- fill a byte string with a byte value

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <string.h>

     void *
     memset(void *b, int c, size_t len);