Macro for static std::string object from literal

Question

Suppose I need to call a function foo that takes a const std::string reference from a great number of places in my code:

int foo(const          


        

Answer 1

You may use something like to create your static std::string "in place":

#include 
#include 

// Sequence of char
template  struct char_sequence
{
    template  using push_back = char_sequence;
};

// Remove all chars from char_sequence from '\0'
template  struct strip_sequence;

template 
struct strip_sequence, Cs...>
{
    using type = char_sequence;
};

template 
struct strip_sequence, Cs2...>
{
    using type = char_sequence;
};

template 
struct strip_sequence, Cs2...>
{
    using type = typename strip_sequence, Cs2..., C>::type;
};

// struct to create a std::string
template  struct static_string;

template 
struct static_string>
{
    static const std::string str;
};

template 
const
std::string static_string>::str = {Cs...};

// helper to get the i_th character (`\0` for out of bound)
template 
constexpr char at(const char (&a)[N]) { return I < N ? a[I] : '\0'; }

// helper to check if the c-string will not be truncated
template 
constexpr bool check_size(const char (&)[N])
{
    static_assert(N <= max_size, "string too long");
    return N <= max_size;
}

// Helper macros to build char_sequence from c-string
#define PUSH_BACK_8(S, I) \
    ::push_back(S)>::push_back(S)> \
    ::push_back(S)>::push_back(S)> \
    ::push_back(S)>::push_back(S)> \
    ::push_back(S)>::push_back(S)>

#define PUSH_BACK_32(S, I) \
        PUSH_BACK_8(S, (I) + 0) PUSH_BACK_8(S, (I) + 8) \
        PUSH_BACK_8(S, (I) + 16) PUSH_BACK_8(S, (I) + 24)

#define PUSH_BACK_128(S, I) \
    PUSH_BACK_32(S, (I) + 0) PUSH_BACK_32(S, (I) + 32) \
    PUSH_BACK_32(S, (I) + 64) PUSH_BACK_32(S, (I) + 96)

// Macro to create char_sequence from c-string (limited to 128 chars) without leading '\0'
#define MAKE_CHAR_SEQUENCE(S) \
    strip_sequence \
    PUSH_BACK_128(S, 0) \
    ::push_back(S) ? '\0' : '\0'> \
    >::type

// Macro to return an static std::string
#define STATIC_STRING(S) static_string::str

Live example