Fix PR 2514: Do not flag dead initializations for variables initialized to a constant global variable.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@64149 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CheckDeadStores.cpp b/lib/Analysis/CheckDeadStores.cpp
index d5e5f4c..504de3c 100644
--- a/lib/Analysis/CheckDeadStores.cpp
+++ b/lib/Analysis/CheckDeadStores.cpp
@@ -195,8 +195,21 @@
// If x is EVER assigned a new value later, don't issue
// a warning. This is because such initialization can be
// due to defensive programming.
- if (!E->isConstantInitializer(Ctx))
- Report(V, DeadInit, V->getLocation(), E->getSourceRange());
+ if (E->isConstantInitializer(Ctx))
+ return;
+
+ // Special case: check for initializations from constant
+ // variables.
+ //
+ // e.g. extern const int MyConstant;
+ // int x = MyConstant;
+ //
+ if (DeclRefExpr *DRE=dyn_cast<DeclRefExpr>(E->IgnoreParenCasts()))
+ if (VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
+ if (VD->hasGlobalStorage() &&
+ VD->getType().isConstQualified()) return;
+
+ Report(V, DeadInit, V->getLocation(), E->getSourceRange());
}
}
}
diff --git a/test/Analysis/dead-stores.c b/test/Analysis/dead-stores.c
index c72bdcf..7d7b369 100644
--- a/test/Analysis/dead-stores.c
+++ b/test/Analysis/dead-stores.c
@@ -147,3 +147,19 @@
return (x = 10); // expected-warning{{Although the value stored to 'x' is used in the enclosing expression, the value is never actually read from 'x'}}
}
+
+// PR 3514: false positive `dead initialization` warning for init to global
+// http://llvm.org/bugs/show_bug.cgi?id=3514
+extern const int MyConstant;
+int f19(void) {
+ int x = MyConstant; // no-warning
+ x = 1;
+ return x;
+}
+
+int f19b(void) { // FIXME: Should this case be considered the same as f19?
+ const int MyConstant = 0;
+ int x = MyConstant; // expected-warning{{never read}}
+ x = 1;
+ return x;
+}