6.50.4 C++11 constant expressions instead of string literals ¶

With gnu++11 or later the string can also be a compile time constant expression inside parens. The constant expression can return a container with data and size member functions, following similar rules as C++26 static_assert message. Any string is converted to the character set of the source code. When this feature is available the __GXX_CONSTEXPR_ASM__ preprocessor macro is predefined.

#include <string>
constexpr std::string_view genfoo() { return "foo"; }

void function()
{
  asm((genfoo()));
}