1 //===--------------------- cxa_exception_storage.cpp ----------------------===//
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.hpp"
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     }
25 }
26 
27 #elif defined(HAS_THREAD_LOCAL)
28 
29 namespace __cxxabiv1 {
30 
31 namespace {
32     __cxa_eh_globals * __globals () {
33         static thread_local __cxa_eh_globals eh_globals;
34         return &eh_globals;
35         }
36     }
37 
38 extern "C" {
39     __cxa_eh_globals * __cxa_get_globals      () { return __globals (); }
40     __cxa_eh_globals * __cxa_get_globals_fast () { return __globals (); }
41     }
42 }
43 
44 #else
45 
46 #include "abort_message.h"
47 #include "fallback_malloc.h"
48 
49 //  In general, we treat all threading errors as fatal.
50 //  We cannot call std::terminate() because that will in turn
51 //  call __cxa_get_globals() and cause infinite recursion.
52 
53 namespace __cxxabiv1 {
54 namespace {
55     std::__libcpp_tls_key key_;
56     std::__libcpp_exec_once_flag flag_ = _LIBCPP_EXEC_ONCE_INITIALIZER;
57 
58     void _LIBCPP_TLS_DESTRUCTOR_CC destruct_ (void *p) {
59         __free_with_fallback ( p );
60         if ( 0 != std::__libcpp_tls_set ( key_, NULL ) )
61             abort_message("cannot zero out thread value for __cxa_get_globals()");
62         }
63 
64     void construct_ () {
65         if ( 0 != std::__libcpp_tls_create ( &key_, destruct_ ) )
66             abort_message("cannot create thread specific key for __cxa_get_globals()");
67         }
68 }
69 
70 extern "C" {
71     __cxa_eh_globals * __cxa_get_globals () {
72     //  Try to get the globals for this thread
73         __cxa_eh_globals* retVal = __cxa_get_globals_fast ();
74 
75     //  If this is the first time we've been asked for these globals, create them
76         if ( NULL == retVal ) {
77             retVal = static_cast<__cxa_eh_globals*>
78                         (__calloc_with_fallback (1, sizeof (__cxa_eh_globals)));
79             if ( NULL == retVal )
80                 abort_message("cannot allocate __cxa_eh_globals");
81             if ( 0 != std::__libcpp_tls_set ( key_, retVal ) )
82                abort_message("std::__libcpp_tls_set failure in __cxa_get_globals()");
83            }
84         return retVal;
85         }
86 
87     // Note that this implementation will reliably return NULL if not
88     // preceded by a call to __cxa_get_globals().  This is an extension
89     // to the Itanium ABI and is taken advantage of in several places in
90     // libc++abi.
91     __cxa_eh_globals * __cxa_get_globals_fast () {
92     //  First time through, create the key.
93         if (0 != std::__libcpp_execute_once(&flag_, construct_))
94             abort_message("execute once failure in __cxa_get_globals_fast()");
95 //        static int init = construct_();
96         return static_cast<__cxa_eh_globals*>(std::__libcpp_tls_get(key_));
97         }
98 
99 }
100 }
101 #endif
102