Implement __cxa_pure_virtual to avoid undefined symbol error

"undefined symbol: __cxa_pure_virtual" will happen when building
//base/android/linker:chromium_android_linker with
use_clang_coverage = true

It seems we can use infinite loop to avoid this error:
https://stackoverflow.com/questions/920500/what-is-the-purpose-of-cxa-pure-virtual


Bug: 1018780
Change-Id: I97cc0a495320c4ede1ecd43cf1b7816b58646960
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1968050
Commit-Queue: Yun Liu <yliuyliu@google.com>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726178}

third_party/android_crazy_linker/README.chromium

@@ -105,3 +105,5 @@ Local Modifications:
 - Add a document about testing the crazy linker in a Chromium checkout
 
 - Remove unnecessary alignment check for size of area that is about to mmap(2).
+
+- Implement __cxa_pure_virtual to avoid undefined symbol error.

third_party/android_crazy_linker/src/src/crazy_linker_debug.cpp

@@ -6,6 +6,7 @@
 
 #include <errno.h>
 #include <string.h>
+#include <unistd.h>
 
 #ifdef __ANDROID__
 #include <android/log.h>
@@ -17,6 +18,16 @@
 
 namespace crazy {
 
+// Log fatal error and exit.
+void LogFatalAndExit(const char* message) {
+#ifdef __ANDROID__
+  __android_log_write(ANDROID_LOG_FATAL, "crazy_linker", message);
+#else
+  ::write(STDERR_FILENO, message, sizeof(message) - 1);
+#endif
+  _exit(1);
+}
+
 #if CRAZY_DEBUG
 
 namespace {

third_party/android_crazy_linker/src/src/crazy_linker_debug.h

@@ -29,6 +29,9 @@ template <bool> struct CompileAssert { };
 
 namespace crazy {
 
+// Log fatal error and exit.
+void LogFatalAndExit(const char* message);
+
 #if CRAZY_DEBUG
 
 void Log(const char* location, const char* fmt, ...);

third_party/android_crazy_linker/src/src/crazy_linker_shared_library.cpp

@@ -59,6 +59,12 @@
 #define DT_PREINIT_ARRAYSZ 33
 #endif
 
+// Avoid undefined symbol:__cxa_pure_virtual error.
+extern "C" void __cxa_pure_virtual() {
+  static const char kFatalMessage[] = "Pure virtual function was called!";
+  crazy::LogFatalAndExit(kFatalMessage);
+}
+
 namespace crazy {
 
 namespace {

third_party/android_crazy_linker/src/src/crazy_linker_system.cpp

@@ -14,6 +14,7 @@
 #include <android/log.h>
 #endif
 
+#include "crazy_linker_debug.h"
 #include "crazy_linker_util.h"
 
 // Note: unit-testing support files are in crazy_linker_files_mock.cpp
@@ -199,12 +200,7 @@ void* operator new(size_t size) {
   // runtime. Hence our fatal message does not contain the number of
   // bytes requested by the allocation.
   static const char kFatalMessage[] = "Out of memory!";
-#ifdef __ANDROID__
-  __android_log_write(ANDROID_LOG_FATAL, "crazy_linker", kFatalMessage);
-#else
-  ::write(STDERR_FILENO, kFatalMessage, sizeof(kFatalMessage) - 1);
-#endif
-  _exit(1);
+  crazy::LogFatalAndExit(kFatalMessage);
 #if defined(__GNUC__)
   __builtin_unreachable();
 #endif