[aapt2] Fix infinite loop in proguard::CollectLocations

std::set only works correctly when the < comparator is a strict weak
ordering, while UsageLocation::operator< was actually implementing !=.

Bug: 134190468
Change-Id: Icb9407e9c8451f9fcb4eb9b2cea310e3bcaf159e
Tested: aapt2_tests, and b/134190468#comment1
(cherry picked from commit 44fa342eb91b90df7998fa2808e21af75aafaf39)

2 files changed, 12 insertions, 2 deletions

diff --git a/tools/aapt2/java/ProguardRules.h b/tools/aapt2/java/ProguardRules.h
index f9656d112b7b..b15df59f56a6 100644
--- a/tools/aapt2/java/ProguardRules.h
+++ b/tools/aapt2/java/ProguardRules.h
@@ -99,11 +99,13 @@ bool CollectLocations(const UsageLocation& location, const KeepSet& keep_set,
 //
 
 inline bool operator==(const UsageLocation& lhs, const UsageLocation& rhs) {
+  // The "source" member is ignored because we only need "name" for outputting
+  // keep rules; "source" is used for comments.
   return lhs.name == rhs.name;
 }
 
-inline int operator<(const UsageLocation& lhs, const UsageLocation& rhs) {
-  return lhs.name.compare(rhs.name);
+inline bool operator<(const UsageLocation& lhs, const UsageLocation& rhs) {
+  return lhs.name.compare(rhs.name) < 0;
 }
 
 //
diff --git a/tools/aapt2/java/ProguardRules_test.cpp b/tools/aapt2/java/ProguardRules_test.cpp
index 559b07af3e80..25b55ab003b0 100644
--- a/tools/aapt2/java/ProguardRules_test.cpp
+++ b/tools/aapt2/java/ProguardRules_test.cpp
@@ -364,4 +364,12 @@ TEST(ProguardRulesTest, TransitionRulesAreEmitted) {
     "-keep class com.foo.Bar { <init>(android.content.Context, android.util.AttributeSet); }"));
 }
 
+TEST(ProguardRulesTest, UsageLocationComparator) {
+  proguard::UsageLocation location1 = {{"pkg", ResourceType::kAttr, "x"}};
+  proguard::UsageLocation location2 = {{"pkg", ResourceType::kAttr, "y"}};
+
+  EXPECT_EQ(location1 < location2, true);
+  EXPECT_EQ(location2 < location1, false);
+}
+
 }  // namespace aapt