[cfe-commits] r132247 - in /cfe/trunk: include/clang/Basic/SourceManager.h lib/Basic/SourceManager.cpp

[Chandler Carruth]

On Sun, May 29, 2011 at 2:38 PM, Argyrios Kyrtzidis <akyrtzi at gmail.com> wrote:
> I completely agree and the extra info about argument expansion is a great improvement but it still doesn't provide *all* the info a client may need to fully explore a macro expansion.
>
> I think what a client ultimately needs (and hopefully Abramo may offer further insights) is 2 things, a list of all the locations of tokens of the macro expansion and the source location of the macro definition that was responsible for the expansion.

This isn't sufficient for some of our applications, and I don't think
is sufficient to generate these diagnostics.

We also need to know what tokens come from macro arguments as opposed
to the macro definition's tokens.

Currently, the lexer expands function-style macros recursively on
demand. This means that we actually don't have a token sequence
representing the definition of the macro (pre-expansion). I actually
like this because it accurately reflects the defined semantics of the
preprocessor.

What we need are for the source locations of each token in the fully
expanded token stream to accurately represent whether the token was
expanded directly from the macro definition's tokens, or whether it
was expanded first from the argument token stream into the macro
definition token stream, and then back into the final fully-expanded
token stream. That's precisely what my patch does.

I also don't think we need to store any extra info to find the
location of a macro definition. It should be the immediate spelling
location. Macro arguments have a second instantiation record that will
take you back to the original spelling location in the call site, but
its first spelling location step should step into macro definition.

> All info that a client may need can be derived/reconstructed by these 2 pieces of info and we can offer helper routines for the more commonly useful info (e.g. for the position of the macro argument, or the source range of the input to the macro argument).

It's not clear to me how you get the position of the macro argument
without re-lexing... which would be really unfortunate cost.

> We can already get a list of tokens, we just don't expose it to clients; we can provide a list of all the source locations of the macro tokens and the client can derive a list of the spelling locations/tokens.
> We are unable to provide the location of the macro definition responsible for the expansion because we don't keep it anywhere. Maybe add a SourceLocation in InstantiationInfo ?

I think this is already available via the spelling location chain...