From: Erik Verbruggen <erikjv@me.com>
Date: Fri, 28 Oct 2016 08:28:42 +0000 (+0000)
Subject: Sema: do not warn about unused const vars if main file is a header
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2a5ffb8501ba332a3822e48caccfc2d9b516dbcc;p=clang

Sema: do not warn about unused const vars if main file is a header

If we pass a header to libclang, e.g. because it's open in an editor in
an IDE, warnings about unused const vars are not useful: other files
that include the header might use those constants. So when -x *-header
is passed as command-line option, suppress this warning.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@285386 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index 2a3be84263..c2622ecab4 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -865,8 +865,11 @@ void Sema::ActOnEndOfTranslationUnit() {
           Diag(DiagD->getLocation(), diag::warn_unneeded_internal_decl)
                 << /*variable*/1 << DiagD->getDeclName();
         } else if (DiagD->getType().isConstQualified()) {
-          Diag(DiagD->getLocation(), diag::warn_unused_const_variable)
-              << DiagD->getDeclName();
+          const SourceManager &SM = SourceMgr;
+          if (SM.getMainFileID() != SM.getFileID(DiagD->getLocation()) ||
+              !PP.getLangOpts().IsHeaderFile)
+            Diag(DiagD->getLocation(), diag::warn_unused_const_variable)
+                << DiagD->getDeclName();
         } else {
           Diag(DiagD->getLocation(), diag::warn_unused_variable)
               << DiagD->getDeclName();
diff --git a/test/Sema/no-warn-unused-const-variables.c b/test/Sema/no-warn-unused-const-variables.c
new file mode 100644
index 0000000000..73cfd8ea71
--- /dev/null
+++ b/test/Sema/no-warn-unused-const-variables.c
@@ -0,0 +1,4 @@
+// RUN: %clang_cc1 -fsyntax-only -Wunused-const-variable -x c-header -ffreestanding -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wunused-const-variable -x c++-header -ffreestanding -verify %s
+// expected-no-diagnostics
+static const int unused[] = { 2, 3, 5, 7, 11, 13 };