C++ compilers can manipulate and create string literals at compile time

test.cc

#include <type_traits>

#include <cstring>
#include <cstdio>

template <size_t N>
class StaticallySizedString {
  char _str[N + 1];

public:
  template <size_t a_size, size_t b_size,
            typename std::enable_if<a_size + b_size == N>::type * = nullptr>
  StaticallySizedString(const StaticallySizedString<a_size> & a,
                        const StaticallySizedString<b_size> & b) {
    std::memcpy(_str, a.c_str(), a_size);
    std::memcpy((char *) _str + a_size, b.c_str(), b_size);
    _str[a_size + b_size] = '\0';
  }

  StaticallySizedString(const char *f) {
    std::memcpy(_str, f, sizeof(_str));
  }

  template <size_t other_n>
  StaticallySizedString<N + other_n>
  operator+(const StaticallySizedString<other_n> & other) const {
    return StaticallySizedString<N + other_n>(*this, other);
  }

  const char *c_str() const {
    return _str;
  }
};

template <size_t N>
StaticallySizedString<N - 1>
make_static_string(const char (&str)[N]) {
  return StaticallySizedString<N - 1>(str);
}

int main(int argc, char *argv[]) {
  // because StaticallySizedString's storage is known at compile time
  // (it's not a pointer to malloc'd memory)
  // the following will be run at compile-time
  // (does not work with std::string)
  auto hai = make_static_string("abbb") + make_static_string("b");
  // this would fail:
  // make_static_string(argv[0])
  std::printf("%s\n", hai.c_str());
  return 0;
}

/*
$ g++ -v
Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.0.0
Thread model: posix
$ g++ -std=c++11 -O3 -S test.cc
$ cat test.s
	.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
	subq	$16, %rsp
	movw	$98, -4(%rbp)
	movl	$1650614881, -8(%rbp)   ## imm = 0x62626261
	leaq	-8(%rbp), %rdi
	callq	_puts
	xorl	%eax, %eax
	addq	$16, %rsp
	popq	%rbp
	ret
	.cfi_endproc

.subsections_via_symbols
   */