[PATCH] D54349: [clang-tidy] new check 'readability-redundant-preprocessor'

[Umann Kristóf via Phabricator via cfe-commits]

Szelethus added inline comments.


================
Comment at: clang-tidy/readability/RedundantPreprocessorCheck.cpp:56-59
+    StringRef SourceText =
+        Lexer::getSourceText(CharSourceRange::getTokenRange(ConditionRange),
+                             PP.getSourceManager(), PP.getLangOpts());
+    std::string Condition = getCondition(SourceText);
----------------
vmiklos wrote:
> Szelethus wrote:
> > I'm a little confused. To me, it seems like you acquired the condition already -- doesn't `ConditionRange` actually cover the, well, condition range? This is how I imagined it:
> > 
> > ```
> > #ifdef CUTE_PANDA_CUBS
> >        ^~~~~~~~~~~~~~~
> >        ConditionRange
> > ```
> > Why is there a need for `getCondition`? Is there any? If there is (maybe the acquired text contains other things), can you document it? I haven't played with `PPCallbacks` much, so I'm fine with being in the wrong.
> ConditionRange covers more than what you expect:
> 
> ```
> #if FOO == 4
>    ^~~~~~~~~
> void f();
> ~~~~~~~~~
> #endif
> ~~~~~~
> ```
> 
> to find out if the condition of the `#if` is the same as a previous one, I want to extract just `FOO == 4` from that, then deal with that part similar to `#ifdef` and `#ifndef`, which are easier as you have a single Token for the condition. But you're right, I should add a comment explaining this.
Oh my god. There is no tool or a convenient method for this??? I had the displeasure of working with the preprocessor in the last couple months, and I get shocked by things like this almost every day.

Yea, unfortunately you will have to write excessive amount of comments to counterweights the shortcomings of `Preprocessor` :/


https://reviews.llvm.org/D54349