Only overwrite destination points-to-set if we have a single object on the LHS.
Adds multiple tests; of these, Overwrite_MultipleDestinations fails before this
change.
PiperOrigin-RevId: 453662886
diff --git a/lifetime_analysis/test/basic.cc b/lifetime_analysis/test/basic.cc
index d442510..d9f2f84 100644
--- a/lifetime_analysis/test/basic.cc
+++ b/lifetime_analysis/test/basic.cc
@@ -456,6 +456,54 @@
LifetimesAre({{"f", "a -> a"}, {"target", "a -> a"}}));
}
+TEST_F(LifetimeAnalysisTest, Overwrite_SingleDestination) {
+ EXPECT_THAT(GetLifetimes(R"(
+ int* target(int* a, int* b) {
+ int** pp = &b;
+ // There is only one thing that `pp` can be pointing at, so the analysis
+ // should conclude that `b` is being overwritten with `a`.
+ *pp = a;
+ return b;
+ }
+ )"),
+ LifetimesAre({{"target", "a, b -> a"}}));
+}
+
+TEST_F(LifetimeAnalysisTest, Overwrite_SingleDestinationVariant) {
+ EXPECT_THAT(GetLifetimes(R"(
+ // Similar to above, but potentially leave `pp` uninitialized.
+ int* target(int* a, int* b) {
+ int** pp;
+ if (*a > 0) {
+ pp = &b;
+ }
+ // If `pp` is uninitialized, the following is UB, so the analysis can
+ // assume that `pp` was initialized to point to `b`.
+ // This particular test function is pretty terrible style, but it seems
+ // plausible that similar situations can come up in more reasonable code.
+ *pp = a;
+ return b;
+ }
+ )"),
+ LifetimesAre({{"target", "a, b -> a"}}));
+}
+
+TEST_F(LifetimeAnalysisTest, Overwrite_MultipleDestinations) {
+ EXPECT_THAT(GetLifetimes(R"(
+ // This is a regression test. The analysis used to conclude falsely that `b`
+ // was unconditionally being overwritten with `a` in the assignment and was
+ // therefore producing the wrong lifetimes "a, b -> a".
+ int* target(int* a, int* b) {
+ int** pp = *a > 0? &a : &b;
+ // The analysis should understand that the following assignment _might_
+ // overwrite `b` with `a` but does not necessarily do so.
+ *pp = a;
+ return b;
+ }
+ )"),
+ LifetimesAre({{"target", "a, a -> a"}}));
+}
+
} // namespace
} // namespace lifetimes
} // namespace tidy
