[PATCH] D116425: [clang-tidy] Improve modernize-redundant-void-arg to recognize macro uses

[Aaron Ballman via Phabricator via cfe-commits]

aaron.ballman added inline comments.


================
Comment at: clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp:51
                      this);
-  Finder->addMatcher(typedefNameDecl().bind(TypedefId), this);
+  Finder->addMatcher(typedefNameDecl(unless(isImplicit())).bind(TypedefId), this);
   auto ParenFunctionType = parenType(innerType(functionType()));
----------------
Might as well fix the clang-format issue.


================
Comment at: clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp:149
   Token ProtoToken;
+  IdentifierTable &Idents = Result.Context->Idents;
+  int MacroLevel = 0;
----------------
I think a safer interface to this is to use a `const IdentifierTable &` here and in `isMacroIdentifier()`. Then, in `isMacroIdentifier()`, instead of using `get()` (which has no `const` overload because it can add an identifier to the table), you can use `find()`. This removes any possibility of accidentally adding identifiers to the table (even in future refactorings).


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Comment at: clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp:157-161
+      if (ProtoToken.is(tok::TokenKind::l_paren)) {
+        State = TokenState::LeftParen;
+      } else if (isMacroIdentifier(Idents, ProtoToken)) {
+        State = TokenState::MacroId;
+      }
----------------



================
Comment at: clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp:164-168
       if (ProtoToken.is(tok::TokenKind::l_paren)) {
-        State = SawLeftParen;
+        State = TokenState::MacroLeftParen;
+      } else {
+        State = TokenState::Start;
+      }
----------------



================
Comment at: clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp:173-177
+        if (isMacroIdentifier(Idents, ProtoToken)) {
+          State = TokenState::MacroId;
+        } else {
+          State = TokenState::MacroArguments;
+        }
----------------



================
Comment at: clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp:180-184
+        if (MacroLevel == 0) {
+          State = TokenState::Start;
+        } else {
+          State = TokenState::MacroId;
+        }
----------------



================
Comment at: clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp:215-219
       if (ProtoToken.is(tok::TokenKind::r_paren)) {
         removeVoidToken(VoidToken, Diagnostic);
       } else if (ProtoToken.is(tok::TokenKind::l_paren)) {
-        State = SawLeftParen;
+        State = TokenState::LeftParen;
       }
----------------



================
Comment at: clang-tools-extra/clang-tidy/modernize/RedundantVoidArgCheck.cpp:224-226
+  if (State == TokenState::Void && ProtoToken.is(tok::TokenKind::r_paren)) {
     removeVoidToken(VoidToken, Diagnostic);
   }
----------------



================
Comment at: clang-tools-extra/test/clang-tidy/checkers/modernize-redundant-void-arg.cpp:202
 // intentionally not LLVM style to check preservation of whitespace
+// clang-format off
 typedef
----------------
Unrelated change can be split out an NFC commit if you'd like, but we don't typically attempt to clang-format existing test files, so also not really necessary either.


================
Comment at: clang-tools-extra/test/clang-tidy/checkers/modernize-redundant-void-arg.cpp:561
+#define return_t(T) T
+return_t(void) func(void);
+// CHECK-MESSAGES: :[[@LINE-1]]:21: warning: redundant void argument list in function declaration
----------------
LegalizeAdulthood wrote:
> jrtc27 wrote:
> > LegalizeAdulthood wrote:
> > > LegalizeAdulthood wrote:
> > > > aaron.ballman wrote:
> > > > > LegalizeAdulthood wrote:
> > > > > > aaron.ballman wrote:
> > > > > > > Can you also add a test for:
> > > > > > > ```
> > > > > > > void func(return_t(void));
> > > > > > > ```
> > > > > > `:-)`
> > > > > > 
> > > > > > What are you suggesting the result should be?  Honestly, looking at that, I'm not sure myself `:)`
> > > > > > 
> > > > > > IMO, if I saw this in a code review, I would flag it because you're using a macro called "return type" to specify the type of an argument.
> > > > > LoL, yeah, the name `return_t` would certainly be novel to use in a parameter list, but what I was hoping to test is whether we try to fix the use of the macro within the parameter list or not. I *think* it probably makes sense to issue the diagnostic, but I don't think it makes sense to try to fix it because the macro could be defined differently for different configurations. But the diagnostic is silenced as well as the fix-it, I wouldn't lose a whole lot of sleep over it.
> > > > Well it could conceivably be used to declare a function pointer argument like this:
> > > > 
> > > > `void func(return_t(void) (*fp)(void));`
> > > > 
> > > > In that case, my expectation is that the check would fix the void arg, but not the arg to the macro.
> > > OK, that was a good idea to add the test I described above because it failed `:)`,
> > > so let me improve the check some more.
> > If you want a less-contrived example that shows up all over the place in crusty old C code that supports (or, perhaps, supported and let bitrot support for) pre-ANSI C compilers:
> > 
> > ```
> > #define __P(x) x
> > void foo __P((void));
> > ```
> > 
> > (the idea being that, for pre-ANSI C compilers, you'd instead define __P(x) as () to get `void foo ();`)
> Well, in (modern) C you don't want to remove the `void` in `(void)` at all.
> 
> This check applies only to C++ code, so we should be safe here.
> 
> I'll add a test case just to cover it -- I think the correct result should be
> that the check leaves this instance of `(void)` intact.
> Well, in (modern) C you don't want to remove the void in (void) at all.

In everything but `-ansi` mode, in fact (C89 supported prototypes). :-D

> I'll add a test case just to cover it -- I think the correct result should be that the check leaves this instance of (void) intact.

Thanks for the coverage, and I agree, we shouldn't try mucking with a fix in the presence of a macro.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D116425/new/

https://reviews.llvm.org/D116425