libcxxabi/src/cxa_exception_storage.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //
   8 //  This file implements the storage for the "Caught Exception Stack"
   9 //  https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html#cxx-exc-stack
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "cxa_exception.h"
  14
  15 #include <__threading_support>
  16
  17 #if defined(_LIBCXXABI_HAS_NO_THREADS)
  18
  19 namespace __cxxabiv1 {
  20 extern "C" {
  21     static __cxa_eh_globals eh_globals;
  22     __cxa_eh_globals *__cxa_get_globals() { return &eh_globals; }
  23     __cxa_eh_globals *__cxa_get_globals_fast() { return &eh_globals; }
  24 } // extern "C"
  25 } // namespace __cxxabiv1
  26
  27 #elif defined(HAS_THREAD_LOCAL)
  28
  29 namespace __cxxabiv1 {
  30 namespace {
  31     __cxa_eh_globals *__globals() {
  32         static thread_local __cxa_eh_globals eh_globals;
  33         return &eh_globals;
  34     }
  35 } // namespace
  36
  37 extern "C" {
  38     __cxa_eh_globals *__cxa_get_globals() { return __globals(); }
  39     __cxa_eh_globals *__cxa_get_globals_fast() { return __globals(); }
  40 } // extern "C"
  41 } // namespace __cxxabiv1
  42
  43 #else
  44
  45 #include "abort_message.h"
  46 #include "fallback_malloc.h"
  47
  48 #if defined(__ELF__) && defined(_LIBCXXABI_LINK_PTHREAD_LIB)
  49 #pragma comment(lib, "pthread")
  50 #endif
  51
  52 //  In general, we treat all threading errors as fatal.
  53 //  We cannot call std::terminate() because that will in turn
  54 //  call __cxa_get_globals() and cause infinite recursion.
  55
  56 namespace __cxxabiv1 {
  57 namespace {
  58     std::__libcpp_tls_key key_;
  59     std::__libcpp_exec_once_flag flag_ = _LIBCPP_EXEC_ONCE_INITIALIZER;
  60
  61     void _LIBCPP_TLS_DESTRUCTOR_CC destruct_(void *p) {
  62         __free_with_fallback(p);
  63         if (0 != std::__libcpp_tls_set(key_, NULL))
  64             abort_message("cannot zero out thread value for __cxa_get_globals()");
  65     }
  66
  67     void construct_() {
  68         if (0 != std::__libcpp_tls_create(&key_, destruct_))
  69             abort_message("cannot create thread specific key for __cxa_get_globals()");
  70     }
  71 } // namespace
  72
  73 extern "C" {
  74     __cxa_eh_globals *__cxa_get_globals() {
  75         // Try to get the globals for this thread
  76         __cxa_eh_globals *retVal = __cxa_get_globals_fast();
  77
  78         // If this is the first time we've been asked for these globals, create them
  79         if (NULL == retVal) {
  80             retVal = static_cast<__cxa_eh_globals*>(
  81                 __calloc_with_fallback(1, sizeof(__cxa_eh_globals)));
  82             if (NULL == retVal)
  83                 abort_message("cannot allocate __cxa_eh_globals");
  84             if (0 != std::__libcpp_tls_set(key_, retVal))
  85                abort_message("std::__libcpp_tls_set failure in __cxa_get_globals()");
  86         }
  87         return retVal;
  88     }
  89
  90     // Note that this implementation will reliably return NULL if not
  91     // preceded by a call to __cxa_get_globals().  This is an extension
  92     // to the Itanium ABI and is taken advantage of in several places in
  93     // libc++abi.
  94     __cxa_eh_globals *__cxa_get_globals_fast() {
  95         // First time through, create the key.
  96         if (0 != std::__libcpp_execute_once(&flag_, construct_))
  97             abort_message("execute once failure in __cxa_get_globals_fast()");
  98         return static_cast<__cxa_eh_globals*>(std::__libcpp_tls_get(key_));
  99     }
 100 } // extern "C"
 101 } // namespace __cxxabiv1
 102
 103 #endif