Compile-time text concatenation via templates and constexpr. Not exactly clean, but perfectly functional. Intended use is automatic JNI type string construction. Technique is a derivation of this: http://stackoverflow.com/a/16720106/375486

concat.cpp

#include <cstdio>
 
using namespace std;
 
template <size_t dim> struct c_array {
    char value[dim];
};
 
// helper; construct a sequence of non-type template arguments
template <size_t... tt_i > struct seq {};
template <size_t t_n, size_t... tt_i > struct gen_seq : gen_seq < t_n-1, t_n-1, tt_i...> {};
template <size_t... tt_i > struct gen_seq < 0, tt_i... > : seq < tt_i... > {};
 
 
// Concatenate strings by using parameter pack expansion
template < size_t S1, size_t S2, size_t... tt_S1, size_t... tt_S2>
constexpr c_array<S1+S2> concat_internal(seq<tt_S1...>, seq<tt_S2...>, c_array<S1> a1, c_array<S2> a2){
    return {{ a1.value[tt_S1]...,a2.value[tt_S2]...}};
}
 
template < size_t S1, size_t S2>
constexpr c_array<S1+S2> concat(c_array<S1> a1, c_array<S2> a2){
    return concat_internal(gen_seq<S1>{},gen_seq<S2>{},a1,a2);
}
 
template <size_t dim, size_t ...tt>
constexpr c_array<dim> ConstStr_internal(const char * str,seq<tt...>){
    return {{ str[tt]...}};
}
 
template <size_t dim>
constexpr c_array<dim-1> ConstStr(const char (&str)[dim]) {
    return ConstStr_internal<dim-1>(str,gen_seq<dim-1>{});
}
 
constexpr auto arr = ConstStr("Hello");
constexpr auto arr2 = ConstStr(" world.");
constexpr auto arr3 = ConstStr(" Also...");
constexpr auto arr4 = ConstStr(" I think my head is going to");
constexpr auto arr5 = ConstStr(" EXPLODE\0");
 
constexpr auto arr6 = concat(arr,concat(arr2,concat(arr3,concat(arr4,arr5))));
 
int main(){
    printf("%s\n", arr6.value);
}

gistfile1.txt

Generated assembly code:

   .section    __TEXT,__text,regular,pure_instructions
    .globl  _main
    .align  4, 0x90
_main:                                  ## @main
    .cfi_startproc
## BB#0:
    pushq   %rbp
Ltmp2:
    .cfi_def_cfa_offset 16
Ltmp3:
    .cfi_offset %rbp, -16
    movq    %rsp, %rbp
Ltmp4:
    .cfi_def_cfa_register %rbp
    leaq    __ZL4arr6(%rip), %rdi
    callq   _puts
    xorl    %eax, %eax
    popq    %rbp
    ret
    .cfi_endproc

    .section    __TEXT,__const
__ZL4arr6:                              ## @_ZL4arr6
    .ascii   "Hello world Also... I think my head is going to EXPLODE"


.subsections_via_symbols