From: Ted Kremenek Date: Fri, 9 Jan 2009 22:15:01 +0000 (+0000) Subject: Dead stores checker: Don't flag dead stores for self-assignments (common escape hatch... X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3b58786f85aaa173e122f6eaff0b6efa233d59a2;p=clang Dead stores checker: Don't flag dead stores for self-assignments (common escape hatch for 'unused variable' warnings). git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@62010 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/Analysis/CheckDeadStores.cpp b/lib/Analysis/CheckDeadStores.cpp index 51943d5016..cad19f4f93 100644 --- a/lib/Analysis/CheckDeadStores.cpp +++ b/lib/Analysis/CheckDeadStores.cpp @@ -128,16 +128,23 @@ public: if (DeclRefExpr* DR = dyn_cast(B->getLHS())) if (VarDecl *VD = dyn_cast(DR->getDecl())) { + Expr* RHS = B->getRHS()->IgnoreParenCasts(); + // Special case: check for assigning null to a pointer. // This is a common form of defensive programming. if (VD->getType()->isPointerType()) { - if (IntegerLiteral* L = - dyn_cast(B->getRHS()->IgnoreParenCasts())) + if (IntegerLiteral* L = dyn_cast(RHS)) // FIXME: Probably should have an Expr::isNullPointerConstant. if (L->getValue() == 0) return; } - + // Special case: self-assignments. These are often used to shut up + // "unused variable" compiler warnings. + if (DeclRefExpr* RhsDR = dyn_cast(RHS)) + if (VD == dyn_cast(RhsDR->getDecl())) + return; + + // Otherwise, issue a warning. DeadStoreKind dsk = Parents.isSubExpr(B) ? Enclosing diff --git a/test/Analysis/dead-stores.c b/test/Analysis/dead-stores.c index 71c4e3b28b..7f99499aab 100644 --- a/test/Analysis/dead-stores.c +++ b/test/Analysis/dead-stores.c @@ -127,3 +127,8 @@ int f16(int x) { return x; } +// Self-assignments should not be flagged as dead stores. +int f17() { + int x = 1; + x = x; // no-warning +}