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1//
2// dup2.cpp
3//
4// Copyright (c) Microsoft Corporation. All rights reserved.
5//
6// Defines _dup2() and _dup2_nolock, which duplicate lowio file handles
7//
8#include <corecrt_internal_lowio.h>
9#include <corecrt_internal_ptd_propagation.h>
10
11static int __cdecl _dup2_nolock_internal(int const source_fh, int const target_fh, __crt_cached_ptd_host& ptd) throw()
12{
13 if ((_osfile(source_fh) & FOPEN) == 0)
14 {
15 // If the source handle is not open, return an error. Noe that the
16 // DuplicateHandle API will not detect this error, because it implies
17 // that _osfhnd(source_fh) == INVALID_HANDLE_VALUE, and this is a
18 // legal HANDLE value to be duplicated.
19 ptd.get_errno().set(EBADF);
20 ptd.get_doserrno().set(0);
21 _ASSERTE(("Invalid file descriptor. File possibly closed by a different thread",0));
22 return -1;
23 }
24
25 // Duplicate the source file onto the target file:
26 intptr_t new_osfhandle;
27
28 BOOL const result = DuplicateHandle(
29 GetCurrentProcess(),
30 reinterpret_cast<HANDLE>(_get_osfhandle(source_fh)),
31 GetCurrentProcess(),
32 &reinterpret_cast<HANDLE&>(new_osfhandle),
33 0,
34 TRUE,
35 DUPLICATE_SAME_ACCESS);
36
37 if (!result)
38 {
39 __acrt_errno_map_os_error_ptd(GetLastError(), ptd);
40 return -1;
41 }
42
43 // If the target is open, close it once we know the OS handle was duplicated successfully.
44 // We ignore the possibility of an error here: an error simply means that the OS handle
45 // value may remain bound for the duration of the process.
46 if (_osfile(target_fh) & FOPEN)
47 {
48 _close_nolock_internal(target_fh, ptd);
49 }
50
51 __acrt_lowio_set_os_handle(target_fh, new_osfhandle);
52
53 // Copy the _osfile information, with the FNOINHERIT bit cleared:
54 _osfile(target_fh) = _osfile(source_fh) & ~FNOINHERIT;
55 _textmode(target_fh) = _textmode(source_fh);
56 _tm_unicode(target_fh) = _tm_unicode(source_fh);
57
58 return 0;
59}
60
61static int __cdecl _dup2_internal(int const source_fh, int const target_fh, __crt_cached_ptd_host& ptd) throw()
62{
63 _UCRT_CHECK_FH_CLEAR_OSSERR_RETURN(ptd, source_fh, EBADF, -1);
64 _UCRT_VALIDATE_CLEAR_OSSERR_RETURN(ptd, (source_fh >= 0 && (unsigned)source_fh < (unsigned)_nhandle), EBADF, -1);
65 _UCRT_VALIDATE_CLEAR_OSSERR_RETURN(ptd, (_osfile(source_fh) & FOPEN), EBADF, -1);
66 _UCRT_CHECK_FH_CLEAR_OSSERR_RETURN(ptd, target_fh, EBADF, -1);
67 _UCRT_VALIDATE_CLEAR_OSSERR_RETURN(ptd, ((unsigned)target_fh < _NHANDLE_), EBADF, -1);
68
69 // Make sure there is an __crt_lowio_handle_data struct corresponding to the target_fh:
70 if (target_fh >= _nhandle && __acrt_lowio_ensure_fh_exists(target_fh) != 0)
71 {
72 return -1;
73 }
74
75 // If the source and target are the same, return success (we've already
76 // verified that the file handle is open, above). This is for conformance
77 // with the POSIX specification for dup2.
78 if (source_fh == target_fh)
79 {
80 return 0;
81 }
82
83 // Obtain the two file handle locks. In order to prevent deadlock, we
84 // always obtain the lock for the lower-numbered file handle first:
85 if (source_fh < target_fh)
86 {
87 __acrt_lowio_lock_fh(source_fh);
88 __acrt_lowio_lock_fh(target_fh);
89 }
90 else if (source_fh > target_fh)
91 {
92 __acrt_lowio_lock_fh(target_fh);
93 __acrt_lowio_lock_fh(source_fh);
94 }
95
96 int result = 0;
97
98 __try
99 {
100 result = _dup2_nolock_internal(source_fh, target_fh, ptd);
101 }
102 __finally
103 {
104 // The order in which we unlock the file handles does not matter:
105 __acrt_lowio_unlock_fh(source_fh);
106 __acrt_lowio_unlock_fh(target_fh);
107 }
108 __endtry
109 return result;
110}
111
112// _dup2() makes the target file handle a duplicate of the source file handle,
113// so that both handles refer to the same file. If the target handle is open
114// upon entry, it is closed so that it is not leaked.
115//
116// Returns 0 if successful; returns -1 and sets errno on failure.
117extern "C" int __cdecl _dup2(int const source_fh, int const target_fh)
118{
119 __crt_cached_ptd_host ptd;
120 return _dup2_internal(source_fh, target_fh, ptd);
121}