Remove warning in dead stores checker for
dead stores within nested assignments. I have
never seen an actual bug found by this specific
warning, and it can lead to many false positives.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@123394 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/StaticAnalyzer/Checkers/CheckDeadStores.cpp b/lib/StaticAnalyzer/Checkers/CheckDeadStores.cpp
index 1fe40c5..96c0dd4 100644
--- a/lib/StaticAnalyzer/Checkers/CheckDeadStores.cpp
+++ b/lib/StaticAnalyzer/Checkers/CheckDeadStores.cpp
@@ -1,4 +1,4 @@
-//==- DeadStores.cpp - Check for stores to dead variables --------*- C++ -*-==//
+//==- DeadStoresChecker.cpp - Check for stores to dead variables -*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
@@ -70,11 +70,10 @@
break;
case Enclosing:
- BugType = "Dead nested assignment";
- msg = "Although the value stored to '" + name +
- "' is used in the enclosing expression, the value is never actually"
- " read from '" + name + "'";
- break;
+ // Don't report issues in this case, e.g.: "if (x = foo())",
+ // where 'x' is unused later. We have yet to see a case where
+ // this is a real bug.
+ return;
}
BR.EmitBasicReport(BugType, "Dead store", msg, L, R);
diff --git a/test/Analysis/dead-stores.c b/test/Analysis/dead-stores.c
index c150fa0..a07138e 100644
--- a/test/Analysis/dead-stores.c
+++ b/test/Analysis/dead-stores.c
@@ -75,9 +75,11 @@
return 1;
}
+// Don't warn for dead stores in nested expressions. We have yet
+// to see a real bug in this scenario.
int f8(int *p) {
extern int *baz();
- if ((p = baz())) // expected-warning{{Although the value}}
+ if ((p = baz())) // no-warning
return 1;
return 0;
}
@@ -148,9 +150,11 @@
int z[count]; // expected-warning{{unused variable 'z'}}
}
+// Don't warn for dead stores in nested expressions. We have yet
+// to see a real bug in this scenario.
int f16(int x) {
x = x * 2;
- x = sizeof(int [x = (x || x + 1) * 2]) // expected-warning{{Although the value stored to 'x' is used}} expected-warning{{The left operand to '*' is always 1}} expected-warning{{The left operand to '+' is always 0}}
+ x = sizeof(int [x = (x || x + 1) * 2]) // expected-warning{{The left operand to '+' is always 0}} expected-warning{{The left operand to '*' is always 1}}
? 5 : 8;
return x;
}
@@ -175,7 +179,9 @@
x = 10; // expected-warning{{Value stored to 'x' is never read}}
while (1);
- 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'}}
+ // Don't warn for dead stores in nested expressions. We have yet
+ // to see a real bug in this scenario.
+ return (x = 10); // no-warning
}
// PR 3514: false positive `dead initialization` warning for init to global