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1//
2// strerror.cpp
3//
4// Copyright (c) Microsoft Corporation. All rights reserved.
5//
6// Defines the strerror() family of functions, which convert an errno error code
7// to a string representation. Note that there are legacy implementations of
8// these functions, prefixed with underscores, in _strerr.cpp. The functions in
9// this file are implemented per the C Standard Library specification.
10//
11#include <corecrt_internal.h>
12#include <malloc.h>
13#include <stddef.h>
14#include <stdlib.h>
15#include <string.h>
16
17
18
19// These functions return the error string to be used when we are unable to return
20// the actual error string.
21_Ret_z_
22static char* get_failure_string(char) throw()
23{
24 return const_cast<char*>("Visual C++ CRT: Not enough memory to complete call to strerror.");
25}
26
27_Ret_z_
28static wchar_t* get_failure_string(wchar_t) throw()
29{
30 return const_cast<wchar_t*>(L"Visual C++ CRT: Not enough memory to complete call to strerror.");
31}
32
33
34
35// These functions return a reference to the thread-local pointer to the buffer
36// to be used to store the error string.
37static char*& get_ptd_buffer(__acrt_ptd* const ptd, char) throw()
38{
39 return ptd->_strerror_buffer;
40}
41
42static wchar_t*& get_ptd_buffer(__acrt_ptd* const ptd, wchar_t) throw()
43{
44 return ptd->_wcserror_buffer;
45}
46
47
48
49// These functions copy the narrow string into the provided buffer.
50_Success_(return == 0)
51static errno_t copy_string_into_buffer(
52 _In_reads_or_z_(max_count) char const* const string,
53 _Out_writes_z_(buffer_count) char* const buffer,
54 size_t const buffer_count,
55 size_t const max_count
56 ) throw()
57{
58 return strncpy_s(buffer, buffer_count, string, max_count);
59}
60
61_Success_(return == 0)
62static errno_t copy_string_into_buffer(
63 _In_reads_or_z_(max_count) char const* const string,
64 _Out_writes_z_(buffer_count) wchar_t* const buffer,
65 size_t const buffer_count,
66 size_t const max_count
67 ) throw()
68{
69 return mbstowcs_s(nullptr, buffer, buffer_count, string, max_count);
70}
71
72
73
74// Maps an error number to an error message string. The error number should be
75// one of the errno values. The string is valid until the next call (on this
76// thread) to one of the strerror functions. The CRT owns the string.
77template <typename Character>
78_Ret_z_
79static Character* __cdecl common_strerror(int const error_number)
80{
81 __acrt_ptd* const ptd = __acrt_getptd_noexit();
82 if (!ptd)
83 return get_failure_string(Character());
84
85 Character*& buffer = get_ptd_buffer(ptd, Character());
86 if (!buffer)
87 buffer = _calloc_crt_t(Character, strerror_buffer_count).detach();
88
89 if (!buffer)
90 return get_failure_string(Character());
91
92 _ERRCHECK(copy_string_into_buffer(_get_sys_err_msg(error_number), buffer, strerror_buffer_count, strerror_buffer_count - 1));
93 return buffer;
94}
95
96extern "C" char* __cdecl strerror(int const error_number)
97{
98 return common_strerror<char>(error_number);
99}
100
101extern "C" wchar_t* __cdecl _wcserror(int const error_number)
102{
103 return common_strerror<wchar_t>(error_number);
104}
105
106
107
108// Maps an error number to an error message string. The error number should be
109// one of the errno values. The string is copied into the provided buffer. On
110// success or truncation, 0 is returned. Otherwise, an error code is returned.
111template <typename Character>
112static errno_t __cdecl common_strerror_s(
113 _Out_writes_z_(buffer_count) Character* const buffer,
114 size_t const buffer_count,
115 int const error_number
116 )
117{
118 _VALIDATE_RETURN_ERRCODE(buffer != nullptr, EINVAL);
119 _VALIDATE_RETURN_ERRCODE(buffer_count > 0, EINVAL);
120
121 errno_t const result = _ERRCHECK_EINVAL_ERANGE(copy_string_into_buffer(
122 _get_sys_err_msg(error_number),
123 buffer,
124 buffer_count,
125 _TRUNCATE));
126
127 return result == STRUNCATE ? 0 : result;
128}
129
130extern "C" errno_t __cdecl strerror_s(
131 char* const buffer,
132 size_t const buffer_count,
133 int const error_number
134 )
135{
136 return common_strerror_s(buffer, buffer_count, error_number);
137}
138
139extern "C" errno_t __cdecl _wcserror_s(
140 wchar_t* const buffer,
141 size_t const buffer_count,
142 int const error_number
143 )
144{
145 return common_strerror_s(buffer, buffer_count, error_number);
146}