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      1 // Copyright (C) 2012 The Android Open Source Project
      2 // All rights reserved.
      3 //
      4 // Redistribution and use in source and binary forms, with or without
      5 // modification, are permitted provided that the following conditions
      6 // are met:
      7 // 1. Redistributions of source code must retain the above copyright
      8 //    notice, this list of conditions and the following disclaimer.
      9 // 2. Redistributions in binary form must reproduce the above copyright
     10 //    notice, this list of conditions and the following disclaimer in the
     11 //    documentation and/or other materials provided with the distribution.
     12 // 3. Neither the name of the project nor the names of its contributors
     13 //    may be used to endorse or promote products derived from this software
     14 //    without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
     17 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     18 // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     19 // ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
     20 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     21 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     22 // OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     23 // HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     24 // LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     25 // OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     26 // SUCH DAMAGE.
     27 
     28 #include <cstdlib>
     29 #include <exception>
     30 #include "cxxabi_defines.h"
     31 
     32 namespace {
     33 
     34 std::terminate_handler current_terminate = __gabixx::__default_terminate;
     35 std::unexpected_handler current_unexpected = __gabixx::__default_unexpected;
     36 
     37 }  // namespace
     38 
     39 
     40 namespace __gabixx {
     41 
     42 // The default std::unexpected() implementation will delegate to
     43 // std::terminate() so that the user-defined std::terminate() handler can
     44 // get the chance to be invoked.
     45 //
     46 _GABIXX_NORETURN void __default_unexpected(void) {
     47   std::terminate();
     48 }
     49 
     50 // The default std::terminate() implementation will crash the process.
     51 // This is done to help debugging, i.e.:
     52 //   - When running the program in a debugger, it's trivial to get
     53 //     a complete stack trace explaining the failure.
     54 //
     55 //   - Otherwise, the default SIGSEGV handler will generate a stack
     56 //     trace in the log, that can later be processed with ndk-stack
     57 //     and other tools.
     58 //
     59 //   - Finally, this also works when a custom SIGSEGV handler has been
     60 //     installed. E.g. when using Google Breakpad, the termination will
     61 //     be recorded in a Minidump, which contains a stack trace to be
     62 //     later analyzed.
     63 //
     64 // The C++ specification states that the default std::terminate()
     65 // handler is library-specific, even though most implementation simply
     66 // choose to call abort() in this case.
     67 //
     68 _GABIXX_NORETURN void __default_terminate(void) {
     69   // The crash address is just a "magic" constant that can be used to
     70   // identify stack traces (like 0xdeadbaad is used when heap corruption
     71   // is detected in the C library). 'cab1' stands for "C++ ABI" :-)
     72   *(reinterpret_cast<char*>(0xdeadcab1)) = 0;
     73 
     74   // should not be here, but just in case.
     75   abort();
     76 }
     77 
     78 _GABIXX_NORETURN void __terminate(std::terminate_handler handler) {
     79   if (!handler)
     80     handler = __default_terminate;
     81 
     82 #if _GABIXX_HAS_EXCEPTIONS
     83   try {
     84     (*handler)();
     85   } catch (...) {
     86     /* nothing */
     87   }
     88 #else
     89   (*handler)();
     90 #endif
     91   __default_terminate();
     92 }
     93 
     94 }  // namespace __gabixx
     95 
     96 namespace std {
     97 
     98 terminate_handler get_terminate() _GABIXX_NOEXCEPT {
     99   return __gabixx_sync_load(&current_terminate);
    100 }
    101 
    102 terminate_handler set_terminate(terminate_handler f) _GABIXX_NOEXCEPT {
    103   if (!f)
    104     f = __gabixx::__default_terminate;
    105 
    106   return __gabixx_sync_swap(&current_terminate, f);
    107 }
    108 
    109 _GABIXX_NORETURN void terminate() _GABIXX_NOEXCEPT_CXX11_ONLY {
    110   __gabixx::__terminate(std::get_terminate());
    111 }
    112 
    113 unexpected_handler get_unexpected() _GABIXX_NOEXCEPT {
    114   return __gabixx_sync_load(&current_unexpected);
    115 }
    116 
    117 unexpected_handler set_unexpected(unexpected_handler f) _GABIXX_NOEXCEPT {
    118   if (!f)
    119     f = __gabixx::__default_terminate;
    120 
    121   return __gabixx_sync_swap(&current_unexpected, f);
    122 }
    123 
    124 _GABIXX_NORETURN void unexpected() {
    125   unexpected_handler handler = std::get_unexpected();
    126   if (handler)
    127     (*handler)();
    128 
    129   // If the handler returns, then call terminate().
    130   terminate();
    131 }
    132 
    133 } // namespace std
    134