[cfe-commits] r62010 - in /cfe/trunk: lib/Analysis/CheckDeadStores.cpp test/Analysis/dead-stores.c
Ted Kremenek
kremenek at apple.com
Fri Jan 9 14:15:01 PST 2009
Author: kremenek
Date: Fri Jan 9 16:15:01 2009
New Revision: 62010
URL: http://llvm.org/viewvc/llvm-project?rev=62010&view=rev
Log:
Dead stores checker: Don't flag dead stores for self-assignments (common escape hatch for 'unused variable' warnings).
Modified:
cfe/trunk/lib/Analysis/CheckDeadStores.cpp
cfe/trunk/test/Analysis/dead-stores.c
Modified: cfe/trunk/lib/Analysis/CheckDeadStores.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/CheckDeadStores.cpp?rev=62010&r1=62009&r2=62010&view=diff
==============================================================================
--- cfe/trunk/lib/Analysis/CheckDeadStores.cpp (original)
+++ cfe/trunk/lib/Analysis/CheckDeadStores.cpp Fri Jan 9 16:15:01 2009
@@ -128,16 +128,23 @@
if (DeclRefExpr* DR = dyn_cast<DeclRefExpr>(B->getLHS()))
if (VarDecl *VD = dyn_cast<VarDecl>(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<IntegerLiteral>(B->getRHS()->IgnoreParenCasts()))
+ if (IntegerLiteral* L = dyn_cast<IntegerLiteral>(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<DeclRefExpr>(RHS))
+ if (VD == dyn_cast<VarDecl>(RhsDR->getDecl()))
+ return;
+
+ // Otherwise, issue a warning.
DeadStoreKind dsk =
Parents.isSubExpr(B)
? Enclosing
Modified: cfe/trunk/test/Analysis/dead-stores.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/dead-stores.c?rev=62010&r1=62009&r2=62010&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/dead-stores.c (original)
+++ cfe/trunk/test/Analysis/dead-stores.c Fri Jan 9 16:15:01 2009
@@ -127,3 +127,8 @@
return x;
}
+// Self-assignments should not be flagged as dead stores.
+int f17() {
+ int x = 1;
+ x = x; // no-warning
+}
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