From 8050299f5b12a8994f323fa5fcfe9199c12e3acf Mon Sep 17 00:00:00 2001
From: Mathias Agopian <mathias@google.com>
Date: Wed, 8 May 2013 16:04:13 -0700
Subject: [PATCH] new String8, String16 ctors to initialize empty static
 strings with static linkage

when libutils is statically linked, the ordering of the static
initializer is not guaranteed and therefore it's unsafe to use
empty static strings: e.g.:

static String8 sThisStaticStringIsNotSafe;

instead, this new constructor can be used:

static String8 sThisStaticStringIsSafe(kEmptyString);

Change-Id: Ia3daf1cab1c97d021c0ee9c2b394b5e27e8d6c0d
---
 include/utils/String16.h |  9 +++++++++
 include/utils/String8.h  |  9 +++++++++
 libs/utils/String16.cpp  | 13 +++++++++++++
 libs/utils/String8.cpp   | 17 +++++++++++++----
 4 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/include/utils/String16.h b/include/utils/String16.h
index 6d4253d24..d131bfc6a 100644
--- a/include/utils/String16.h
+++ b/include/utils/String16.h
@@ -41,7 +41,16 @@ class TextOutput;
 class String16
 {
 public:
+    /* use String16(StaticLinkage) if you're statically linking against
+     * libutils and declaring an empty static String16, e.g.:
+     *
+     *   static String16 sAStaticEmptyString(String16::kEmptyString);
+     *   static String16 sAnotherStaticEmptyString(sAStaticEmptyString);
+     */
+    enum StaticLinkage { kEmptyString };
+
                                 String16();
+    explicit                    String16(StaticLinkage);
                                 String16(const String16& o);
                                 String16(const String16& o,
                                          size_t len,
diff --git a/include/utils/String8.h b/include/utils/String8.h
index 9426fcfc8..ef5947047 100644
--- a/include/utils/String8.h
+++ b/include/utils/String8.h
@@ -37,7 +37,16 @@ class TextOutput;
 class String8
 {
 public:
+    /* use String8(StaticLinkage) if you're statically linking against
+     * libutils and declaring an empty static String8, e.g.:
+     *
+     *   static String8 sAStaticEmptyString(String8::kEmptyString);
+     *   static String8 sAnotherStaticEmptyString(sAStaticEmptyString);
+     */
+    enum StaticLinkage { kEmptyString };
+
                                 String8();
+    explicit                    String8(StaticLinkage);
                                 String8(const String8& o);
     explicit                    String8(const char* o);
     explicit                    String8(const char* o, size_t numChars);
diff --git a/libs/utils/String16.cpp b/libs/utils/String16.cpp
index c856ceb9b..b09b728ad 100644
--- a/libs/utils/String16.cpp
+++ b/libs/utils/String16.cpp
@@ -93,6 +93,19 @@ String16::String16()
 {
 }
 
+String16::String16(StaticLinkage)
+    : mString(0)
+{
+    // this constructor is used when we can't rely on the static-initializers
+    // having run. In this case we always allocate an empty string. It's less
+    // efficient than using getEmptyString(), but we assume it's uncommon.
+
+    char16_t* data = static_cast<char16_t*>(
+            SharedBuffer::alloc(sizeof(char16_t))->data());
+    data[0] = 0;
+    mString = data;
+}
+
 String16::String16(const String16& o)
     : mString(o.mString)
 {
diff --git a/libs/utils/String8.cpp b/libs/utils/String8.cpp
index 413928abb..e852d77b7 100644
--- a/libs/utils/String8.cpp
+++ b/libs/utils/String8.cpp
@@ -47,16 +47,12 @@ void initialize_string8();
 
 static inline char* getEmptyString()
 {
-    if (!gEmptyStringBuf) initialize_string8();
-
     gEmptyStringBuf->acquire();
     return gEmptyString;
 }
 
 void initialize_string8()
 {
-    if (gEmptyStringBuf) return;
-
     // HACK: This dummy dependency forces linking libutils Static.cpp,
     // which is needed to initialize String8/String16 classes.
     // These variables are named for Darwin, but are needed elsewhere too,
@@ -146,6 +142,19 @@ String8::String8()
 {
 }
 
+String8::String8(StaticLinkage)
+    : mString(0)
+{
+    // this constructor is used when we can't rely on the static-initializers
+    // having run. In this case we always allocate an empty string. It's less
+    // efficient than using getEmptyString(), but we assume it's uncommon.
+
+    char* data = static_cast<char*>(
+            SharedBuffer::alloc(sizeof(char))->data());
+    data[0] = 0;
+    mString = data;
+}
+
 String8::String8(const String8& o)
     : mString(o.mString)
 {