From fc7ff5540412f8003024e1b4940fb8408dff2ca6 Mon Sep 17 00:00:00 2001
From: Ted Kremenek <kremenek@apple.com>
Date: Fri, 25 Jul 2008 04:47:34 +0000
Subject: [PATCH] Don't emit 'dead initialization' warnings for variables
 marked 'unused'. This fixes PR 2573:
 http://llvm.org/bugs/show_bug.cgi?id=2573

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@54009 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/CheckDeadStores.cpp | 12 +++++++++---
 test/Analysis/dead-stores.c      |  9 ++++++++-
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/lib/Analysis/CheckDeadStores.cpp b/lib/Analysis/CheckDeadStores.cpp
index 4ab6680a78..4acacdf0ce 100644
--- a/lib/Analysis/CheckDeadStores.cpp
+++ b/lib/Analysis/CheckDeadStores.cpp
@@ -164,11 +164,16 @@ public:
       for (ScopedDecl* SD = DS->getDecl(); SD; SD = SD->getNextDeclarator()) {
         
         VarDecl* V = dyn_cast<VarDecl>(SD);
-        if (!V) continue;
+
+        if (!V)
+          continue;
         
         if (V->hasLocalStorage())
-          if (Expr* E = V->getInit())
-            if (!Live(V, AD)) {
+          if (Expr* E = V->getInit()) {
+            // A dead initialization is a variable that is dead after it
+            // is initialized.  We don't flag warnings for those variables
+            // marked 'unused'.
+            if (!Live(V, AD) && V->getAttr<UnusedAttr>() == 0) {
               // Special case: check for initializations with constants.
               //
               //  e.g. : int x = 0;
@@ -179,6 +184,7 @@ public:
               if (!E->isConstantExpr(Ctx,NULL))
                 Report(V, DeadInit, V->getLocation(), E->getSourceRange());
             }
+          }
       }
   }
 };
diff --git a/test/Analysis/dead-stores.c b/test/Analysis/dead-stores.c
index dce058c02e..0ca289231b 100644
--- a/test/Analysis/dead-stores.c
+++ b/test/Analysis/dead-stores.c
@@ -77,5 +77,12 @@ int f11() {
   return ++x; // expected-warning{{never read}}
 }
 
-
+int f12a(int y) {
+  int x = y;  // expected-warning{{never read}}
+  return 1;
+}
+int f12b(int y) {
+  int x __attribute__((unused)) = y;  // no-warning
+  return 1;
+}
 
-- 
2.50.1