blob: ea42203d0544693f53af0460732e6da28867062a (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
|
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
// UNSUPPORTED: no-exceptions
// The fix for issue 57964 requires an updated dylib due to explicit
// instantiations. That means Apple backdeployment targets remain broken.
// UNSUPPORTED: using-built-library-before-llvm-19
// <ios>
// class ios_base
// ~ios_base()
//
// Destroying a constructed ios_base object that has not been
// initialized by basic_ios::init is undefined behaviour. This can
// happen in practice, make sure the undefined behaviour is handled
// gracefully.
//
//
// [ios.base.cons]/1
//
// ios_base();
// Effects: Each ios_base member has an indeterminate value after construction.
// The object's members shall be initialized by calling basic_ios::init before
// the object's first use or before it is destroyed, whichever comes first;
// otherwise the behavior is undefined.
//
// [basic.ios.cons]/2
//
// basic_ios();
// Effects: Leaves its member objects uninitialized. The object shall be
// initialized by calling basic_ios::init before its first use or before it is
// destroyed, whichever comes first; otherwise the behavior is undefined.
//
// ostream and friends have a basic_ios virtual base.
// [class.base.init]/13
// In a non-delegating constructor, initialization proceeds in the
// following order:
// - First, and only for the constructor of the most derived class
// ([intro.object]), virtual base classes are initialized ...
//
// So in this example
// struct Foo : AlwaysThrows, std::ostream {
// Foo() : AlwaysThrows{}, std::ostream{nullptr} {}
// };
//
// Here
// - the ios_base object is constructed
// - the AlwaysThrows object is constructed and throws an exception
// - the AlwaysThrows object is destrodyed
// - the ios_base object is destroyed
//
// The ios_base object is destroyed before it has been initialized and runs
// into undefined behavior. By using __loc_ as a sentinel we can avoid
// accessing uninitialized memory in the destructor.
#include <ostream>
struct AlwaysThrows {
AlwaysThrows() { throw 1; }
};
struct Foo : AlwaysThrows, std::ostream {
Foo() : AlwaysThrows(), std::ostream(nullptr) {}
};
int main(int, char**) {
try {
Foo foo;
} catch (...) {
};
return 0;
}
|
