I am wondering how different the preprocessors for C++ and C are.
The reason for the question is this question on a preprocessor-specific question where the paragraph of the standard that addresses the question has a different wording (and a different paragraph number) and also are difference concerning the true and false keywords in C++.
So, are there more differences or is this the only difference.
An extension of the question would be when is a source file emitted differently by a C++ preprocessor and a C preprocessor.
The C++03 preprocessor is (at least intended to be) similar to the C preprocessor before C99. Although the wording and paragraph numbers are slightly different, the only technical differences I'm aware of between the two are that the C++ preprocessor handles digraphs (two-letter alternative tokens) and universal character names, which are not present in C.
As of C99, the C preprocessor added some new capabilities (e.g., variadic macros) that do not exist in the current version of C++. I don't remember for sure, but don't believe that digraphs were added.
I believe C++0x will bring the two in line again (at least that's the intent). Again, the paragraph numbers and wording won't be identical, but I believe the intent is that they should work the same (other than retaining the differences mentioned above).