How does org-mode implement syntax highlighting for code blocks?

Question

How does org-mode implement syntax highlighting for code blocks? More specifically, for a C file, does it use cc-mode or does it have its own algorithm? For example, if I have this org file: test.org:

* Example source code in C: 

#+BEGIN_SRC c
#include <stdio.h>

int main() {
    printf( "Hello world\n" );
    return 0;
}
#+END_SRC

I get the following highlighting:

---

But if have the same pure C file (using cc-mode) test.c:

#include <stdio.h>

int main() {
    printf( "Hello world\n" );
    return 0;
}

I get:

---

---

Notice that printf has different face color in the two files. So it seems like org-mode has its own syntax highlighting. It is not using cc-mode to do the highlighting, is that correct?

Answer 1

It uses cc-mode.

It copes the text to a temporary buffer, highlights it using the major mode that is associated with the language, and copies back the highlighting.

In addition, it makes everything not highlighted grey. In addition to the difference you spotted in printf, this is also visible in other places like the braces and parentheses.