Is strlen of a const char* optimised?

c, optimization, string, strlen

Solution

I don't think you can ever depend on an optimization happening.

Why not do it like this, if you really want to avoid an extra variable:

void send_str(const char *data)
{
  for(size_t i = strlen(data); i != 0; --i)
    send_byte(*data++);
}

Or, less silly, and more like an actual production-quality C program:

void send_str(const char *data)
{
  while(*data != '\0')
    send_byte(*data++);
}

There's no point at all in iterating over the characters twice, so don't call `strlen()` at all, detect the end-of-string yourself.

Problem

Can I use `strlen` of a `const char*` in a loop like this and expect O(n) time complexity, or would it result in O(n^2)? I think it looks cleaner than using a variable for the string length. ``` void send_str( const char* data ) { for (uint8_t i = 0; i < strlen(data); i++) send_byte( data[i] ); } ``` Does it depend on the optimization level?

Original source