[PATCH] D50766: Fix false positive unsequenced access and modification warning in array subscript expression.
Nicolas Lesser via Phabricator via cfe-commits
cfe-commits at lists.llvm.org
Thu Jan 10 11:09:11 PST 2019
This revision was automatically updated to reflect the committed changes.
Closed by commit rC350874: Fix false positive unsequenced access and modification warning in array… (authored by Rakete1111, committed by ).
Repository:
rC Clang
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D50766/new/
https://reviews.llvm.org/D50766
Files:
lib/Sema/SemaChecking.cpp
test/SemaCXX/warn-unsequenced-cxx17.cpp
test/SemaCXX/warn-unsequenced.cpp
Index: test/SemaCXX/warn-unsequenced.cpp
===================================================================
--- test/SemaCXX/warn-unsequenced.cpp
+++ test/SemaCXX/warn-unsequenced.cpp
@@ -81,6 +81,7 @@
int *p = xs;
a = *(a++, p); // ok
a = a++ && a; // ok
+ p[(long long unsigned)(p = 0)]; // expected-warning {{unsequenced modification and access to 'p'}}
A *q = &agg1;
(q = &agg2)->y = q->x; // expected-warning {{unsequenced modification and access to 'q'}}
Index: test/SemaCXX/warn-unsequenced-cxx17.cpp
===================================================================
--- test/SemaCXX/warn-unsequenced-cxx17.cpp
+++ test/SemaCXX/warn-unsequenced-cxx17.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++17 -Wno-unused %s
+
+void test() {
+ int xs[10];
+ int *p = xs;
+ // expected-no-diagnostics
+ p[(long long unsigned)(p = 0)]; // ok
+}
Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -11908,30 +11908,42 @@
notePostUse(O, E);
}
- void VisitBinComma(BinaryOperator *BO) {
- // C++11 [expr.comma]p1:
- // Every value computation and side effect associated with the left
- // expression is sequenced before every value computation and side
- // effect associated with the right expression.
- SequenceTree::Seq LHS = Tree.allocate(Region);
- SequenceTree::Seq RHS = Tree.allocate(Region);
+ void VisitSequencedExpressions(Expr *SequencedBefore, Expr *SequencedAfter) {
+ SequenceTree::Seq BeforeRegion = Tree.allocate(Region);
+ SequenceTree::Seq AfterRegion = Tree.allocate(Region);
SequenceTree::Seq OldRegion = Region;
{
- SequencedSubexpression SeqLHS(*this);
- Region = LHS;
- Visit(BO->getLHS());
+ SequencedSubexpression SeqBefore(*this);
+ Region = BeforeRegion;
+ Visit(SequencedBefore);
}
- Region = RHS;
- Visit(BO->getRHS());
+ Region = AfterRegion;
+ Visit(SequencedAfter);
Region = OldRegion;
- // Forget that LHS and RHS are sequenced. They are both unsequenced
- // with respect to other stuff.
- Tree.merge(LHS);
- Tree.merge(RHS);
+ Tree.merge(BeforeRegion);
+ Tree.merge(AfterRegion);
+ }
+
+ void VisitArraySubscriptExpr(ArraySubscriptExpr *ASE) {
+ // C++17 [expr.sub]p1:
+ // The expression E1[E2] is identical (by definition) to *((E1)+(E2)). The
+ // expression E1 is sequenced before the expression E2.
+ if (SemaRef.getLangOpts().CPlusPlus17)
+ VisitSequencedExpressions(ASE->getLHS(), ASE->getRHS());
+ else
+ Base::VisitStmt(ASE);
+ }
+
+ void VisitBinComma(BinaryOperator *BO) {
+ // C++11 [expr.comma]p1:
+ // Every value computation and side effect associated with the left
+ // expression is sequenced before every value computation and side
+ // effect associated with the right expression.
+ VisitSequencedExpressions(BO->getLHS(), BO->getRHS());
}
void VisitBinAssign(BinaryOperator *BO) {
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