master
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 <__thread/support.h>
16
17#if defined(_LIBCXXABI_HAS_NO_THREADS)
18
19namespace __cxxabiv1 {
20extern "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 __has_feature(cxx_thread_local)
28
29namespace __cxxabiv1 {
30namespace {
31 __cxa_eh_globals *__globals() {
32 static thread_local __cxa_eh_globals eh_globals;
33 return &eh_globals;
34 }
35} // namespace
36
37extern "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
56namespace __cxxabiv1 {
57namespace {
58 std::__libcpp_tls_key key_;
59 constinit 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
73extern "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