result = glfwLoadTexture2D( filename.c_str(), GLFW_BUILD_MIPMAPS_BIT ); code example

Example: c c_str

Get C string equivalent

  TL;DR	->	Makes the string end with '\0'

Returns a pointer to an array that contains a null-terminated sequence of
characters (i.e., a C-string) representing the current value of the string
object.

This array includes the same sequence of characters that make up the value of
the string object plus an additional terminating null-character ('\0') at the
end.