commit 98b396e7854056d7b1b478566e373afb2bc046f6
author Jooyung Han <jooyung@google.com> Sun Jun 27 03:30:42 2021 +0900
committer Jooyung Han <jooyung@google.com> Tue Jun 29 10:18:23 2021 +0900
tree 5f058e6d4f7007cbb7cadae5d4eb8307698f08c4
parent c037bdbc5a1f2b0e0130195030b874c9dfff99ca

String16 is moveable (noexcept)

String16 is still in use by AIDL compiler. Because String16 is not
noexcept-move-constructible, the C++ compiler will complain when it is
used with non-copyable types (such as ParcelFileDescriptor).

For example, when vector<Foo> is resized, copy-ctor of Foo is called,
which is not available.

  parcelable Foo {
    String s;
    ParcelFileDescriptor[] pfds;
  }

By providing noexcept move-ctor for String16, vector<Foo> can be resized
with no problem.

Btw, copy from StaticString16 is specialized for efficiency and move
from StaticString16 don't need to be different from copy.

Bug: 192136980
Test: libutils_test
Change-Id: I13744a2ceebf5781c3ef7f3a04237a6750b0db0a

libutils/String16_test.cpp

diff --git a/libutils/String16_test.cpp b/libutils/String16_test.cpp
index 54662ac..917f1a3 100644
--- a/libutils/String16_test.cpp
+++ b/libutils/String16_test.cpp
@@ -64,6 +64,13 @@
     EXPECT_STR16EQ(u"Verify me", another);
 }
 
+TEST(String16Test, MoveAssign) {
+    String16 tmp("Verify me");
+    String16 another;
+    another = std::move(tmp);
+    EXPECT_STR16EQ(u"Verify me", another);
+}
+
 TEST(String16Test, Size) {
     String16 tmp("Verify me");
     EXPECT_EQ(9U, tmp.size());
@@ -123,6 +130,10 @@
     String16 another(std::move(tmp));
     EXPECT_STR16EQ(u"Verify me", another);
     EXPECT_TRUE(another.isStaticString());
+    // move/copy from StaticString16 is specialized (just copy the handle).
+    // no extra actions required.
+    EXPECT_STR16EQ(u"Verify me", tmp);
+    EXPECT_TRUE(tmp.isStaticString());
 }
 
 TEST(String16Test, StaticStringSize) {
@@ -174,10 +185,16 @@
     EXPECT_STR16EQ(u"Verify me", another);
 }
 
-TEST(String16Test, StringMoveFromStaticString) {
+TEST(String16Test, StringMoveAssignFromStaticString) {
     StaticString16 tmp(u"Verify me");
-    String16 another(std::move(tmp));
+    String16 another(u"nonstatic");
+    another = std::move(tmp);
     EXPECT_STR16EQ(u"Verify me", another);
+    EXPECT_TRUE(another.isStaticString());
+    // move/copy from StaticString16 is specialized (just copy handle).
+    // no extra actions required.
+    EXPECT_STR16EQ(u"Verify me", tmp);
+    EXPECT_TRUE(tmp.isStaticString());
 }
 
 TEST(String16Test, EmptyStringIsStatic) {