[PATCH] D53354: [WIP][NOT FOR COMMIT][PROTOTYPE] clang-scan-deps: dependency scanning tool rough prototype

[Alex Lorenz via Phabricator via cfe-commits]

arphaman added inline comments.


================
Comment at: lib/Lex/FilterToIncludes.cpp:628
+  First = Id.Last;
+  auto Kind = llvm::StringSwitch<TokenKind>(Id.Name)
+                  .Case("include", pp_include)
----------------
arphaman wrote:
> ddunbar wrote:
> > What is our feeling w.r.t. _Pragma, which can in theory influence the preprocessor. I'm not sure this model can sanely support it?
> We need to look into that. In the worst case we can always avoid minimizing the file if it has a _Pragma anywhere in it.
We also have to handle cases like this one:

foo.h:
```
#define PP _Pragma
```

bar.h:
```
PP ("foo")
```

Unfortunately this can't be handled by just disabling minimization for `foo.h` as PP will be stripped out from `bar.h`. Furthermore, this pattern is quite reasonable, so we should expect it in the code we receive. Right now I can't think of a reasonable solution for this problem.

There's also a more "evil" case:

```
#define P(A, B) A##B

P(_Pra,gma)("foo")
```

It would be reasonable to introduce a warning for the use of `_Pragma` token that was created using PP token concatenation and just hope that our users won't use this pattern.


Repository:
  rC Clang

https://reviews.llvm.org/D53354