[cfe-commits] r57554 - in /cfe/trunk: lib/Analysis/CheckDeadStores.cpp test/Analysis/dead-stores.c
Ted Kremenek
kremenek at apple.com
Tue Oct 14 22:23:41 PDT 2008
Author: kremenek
Date: Wed Oct 15 00:23:41 2008
New Revision: 57554
URL: http://llvm.org/viewvc/llvm-project?rev=57554&view=rev
Log:
Enhance dead store checker to not flag preincrements to dead variables where the preincrement is a subexpression, e.g. foo(++x); This can cause false negatives, but will remove a whole class of false positives.
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=57554&r1=57553&r2=57554&view=diff
==============================================================================
--- cfe/trunk/lib/Analysis/CheckDeadStores.cpp (original)
+++ cfe/trunk/lib/Analysis/CheckDeadStores.cpp Wed Oct 15 00:23:41 2008
@@ -149,6 +149,13 @@
else if (UnaryOperator* U = dyn_cast<UnaryOperator>(S)) {
if (!U->isIncrementOp())
return;
+
+ // Handle: ++x within a subexpression. The solution is not warn
+ // about preincrements to dead variables when the preincrement occurs
+ // as a subexpression. This can lead to false negatives, e.g. "(++x);"
+ // A generalized dead code checker should find such issues.
+ if (U->isPrefix() && Parents.isSubExpr(U))
+ return;
Expr *Ex = U->getSubExpr()->IgnoreParenCasts();
Modified: cfe/trunk/test/Analysis/dead-stores.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/dead-stores.c?rev=57554&r1=57553&r2=57554&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/dead-stores.c (original)
+++ cfe/trunk/test/Analysis/dead-stores.c Wed Oct 15 00:23:41 2008
@@ -74,9 +74,15 @@
int f11() {
int x = 4;
- return ++x; // expected-warning{{never read}}
+ return x++; // expected-warning{{never read}}
}
+int f11b() {
+ int x = 4;
+ return ++x; // no-warning
+}
+
+
int f12a(int y) {
int x = y; // expected-warning{{never read}}
return 1;
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