[CodeComplete] suppress define X X macros

[sammccall]

Summary

In particular, stderr etc where the equivalent symbols exist in the global
namespace. Having the symbol instead of the macro helps with ranking, and avoids
the current duplicate stderr suggestions.

@ilya-biryukov: think this is the right way to fix the duplicate completions?
Hiding the shadowed decl might be more correct, but it'd be hard *and* give
unfortunate ranking.

[sammccall]

Hmm, musl does #define stderr (stderr) :-( And they discussed #define stderr (stderr+0).
(To enforce it's not assigned to etc)
https://github.com/cloudius-systems/musl/blob/master/include/stdio.h#L61

Ilya also pointed out offline the windows API convention: CreateFile is a macro for CreateFileW or CreateFileA. In these cases merely suppressing the macro isn't enough, we'd want to replace its info with the underlying decl.

Not sure how/whether to generalize this hack...

[ilya-biryukov]

In D47896#1126171, @sammccall wrote:

Hmm, musl does #define stderr (stderr) :-( And they discussed #define stderr (stderr+0).
(To enforce it's not assigned to etc)
https://github.com/cloudius-systems/musl/blob/master/include/stdio.h#L61

Ilya also pointed out offline the windows API convention: CreateFile is a macro for CreateFileW or CreateFileA. In these cases merely suppressing the macro isn't enough, we'd want to replace its info with the underlying decl.

Not sure how/whether to generalize this hack...

Yeah, I'm not sure. Maybe we should just special-case the known cases...

[sammccall]

Going to put this on hold until someone actually reports the bug.

lib/Sema/SemaCodeComplete.cpp

static void AddMacroResults(Preprocessor &PP, ResultBuilder &Results,
   
   Results.EnterNewScope();
   
   for (Preprocessor::macro_iterator M = PP.macro_begin(), 
                                  MEnd = PP.macro_end();
        M != MEnd; ++M) {
     auto MD = PP.getMacroDefinition(M->first);
     if (IncludeUndefined || MD) {
-      if (MacroInfo *MI = MD.getMacroInfo())
+      if (MacroInfo *MI = MD.getMacroInfo()) {
         if (MI->isUsedForHeaderGuard())
           continue;
+        // Some standard libraries e.g. #define stderr stderr, the underlying
+        // decl is more useful.
+        if (MI->getNumTokens() == 1 && MI->isObjectLike()) {
+          const Token &Tok = MI->getReplacementToken(0);
+          if (Tok.is(tok::identifier) &&
+              Tok.getIdentifierInfo()->getName() == M->first->getName())
+            continue;
+        }
+      }
 
       Results.AddResult(Result(M->first,
                              getMacroUsagePriority(M->first->getName(),
                                                    PP.getLangOpts(),
                                                    TargetTypeIsPointer)));
     }
   }
   

test/Index/complete-macros.c

 #define variadic3(args, ...)
 #define variadic4(first, second, args, ...)
 #define variadic5(first, second, args ...)
 
 void test_variadic() {
   
 }
 
+int shadow;
+#define shadow shadow
+void test_shadow() {
+
+}
+
 // RUN: c-index-test -code-completion-at=%s:7:1 %s -I%S | FileCheck -check-prefix=CHECK-CC0 %s
 // CHECK-CC0-NOT: FOO
 // RUN: env CINDEXTEST_EDITING=1 CINDEXTEST_COMPLETION_CACHING=1 c-index-test -code-completion-at=%s:7:1 %s -I%S | FileCheck -check-prefix=CHECK-CC1 %s
 // CHECK-CC1: macro definition:{TypedText FOO} (70)
 // RUN: c-index-test -code-completion-at=%s:13:13 %s -I%S | FileCheck -check-prefix=CHECK-CC2 %s
 // RUN: c-index-test -code-completion-at=%s:14:8 %s -I%S | FileCheck -check-prefix=CHECK-CC2 %s
 // RUN: env CINDEXTEST_EDITING=1 CINDEXTEST_COMPLETION_CACHING=1 c-index-test -code-completion-at=%s:14:8 %s -I%S | FileCheck -check-prefix=CHECK-CC2 %s
 // CHECK-CC2: macro definition:{TypedText nil} (32)
 // RUN: c-index-test -code-completion-at=%s:15:5 %s -I%S | FileCheck -check-prefix=CHECK-CC3 %s
 // RUN: env CINDEXTEST_EDITING=1 CINDEXTEST_COMPLETION_CACHING=1 c-index-test -code-completion-at=%s:15:5 %s -I%S | FileCheck -check-prefix=CHECK-CC3 %s
 // CHECK-CC3: macro definition:{TypedText nil} (65)
 // RUN: env CINDEXTEST_EDITING=1 CINDEXTEST_COMPLETION_CACHING=1 c-index-test -code-completion-at=%s:25:2 %s -I%S | FileCheck -check-prefix=CHECK-VARIADIC %s
 // CHECK-VARIADIC: macro definition:{TypedText variadic1}{LeftParen (}{Placeholder ...}{RightParen )} (70)
 // CHECK-VARIADIC: macro definition:{TypedText variadic2}{LeftParen (}{Placeholder args...}{RightParen )} (70)
 // CHECK-VARIADIC: macro definition:{TypedText variadic3}{LeftParen (}{Placeholder args, ...}{RightParen )} (70)
 // CHECK-VARIADIC: macro definition:{TypedText variadic4}{LeftParen (}{Placeholder first}{Comma , }{Placeholder second}{Comma , }{Placeholder args, ...}{RightParen )} (70)
 // CHECK-VARIADIC: macro definition:{TypedText variadic5}{LeftParen (}{Placeholder first}{Comma , }{Placeholder second}{Comma , }{Placeholder args...}{RightParen )} (70)
 
 // RUN: env CINDEXTEST_EDITING=1 CINDEXTEST_COMPLETION_CACHING=1 c-index-test -code-completion-at=%s:15:5 %s -I%S | FileCheck -check-prefix=CHECK-CC4 %s
 // CHECK-CC4-NOT: COMPLETE_MACROS_H_GUARD
+
+// RUN: c-index-test -code-completion-at=%s:31:1 %s -I%S | FileCheck -check-prefix=CHECK-SHADOW %s
+// CHECK-SHADOW: FunctionDecl:{ResultType void}{TypedText g}
+// CHECK-SHADOW-NOT: macro definition:{TypedText shadow}