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
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
// _WIN32
// Synopsis
//
// This header provides macros for using FOO_EXPORT macros with explicit
// template instantiation declarations and definitions.
// Generally, the FOO_EXPORT macros are used at declarations,
// and GCC requires them to be used at explicit instantiation declarations,
// but MSVC requires __declspec(dllexport) to be used at the explicit
// instantiation definitions instead.
// Usage
//
// In a header file, write:
//
// extern template class EXPORT_TEMPLATE_DECLARE(FOO_EXPORT) foo<bar>;
//
// In a source file, write:
//
// template class EXPORT_TEMPLATE_DEFINE(FOO_EXPORT) foo<bar>;
// Implementation notes
//
// The implementation of this header uses some subtle macro semantics to
// detect what the provided FOO_EXPORT value was defined as and then
// to dispatch to appropriate macro definitions. Unfortunately,
// MSVC's C preprocessor is rather non-compliant and requires special
// care to make it work.
//
// Issue 1.
//
// #define F(x)
// F()
//
// MSVC emits warning C4003 ("not enough actual parameters for macro
// 'F'), even though it's a valid macro invocation. This affects the
// macros below that take just an "export" parameter, because export
// may be empty.
//
// As a workaround, we can add a dummy parameter and arguments:
//
// #define F(x,_)
// F(,)
//
// Issue 2.
//
// #define F(x) G##x
// #define Gj() ok
// F(j())
//
// The correct replacement for "F(j())" is "ok", but MSVC replaces it
// with "Gj()". As a workaround, we can pass the result to an
// identity macro to force MSVC to look for replacements again. (This
// is why EXPORT_TEMPLATE_STYLE_3 exists.)
// INVOKE is an internal helper macro to perform parameter replacements
// and token pasting to chain invoke another macro. E.g.,
// EXPORT_TEMPLATE_INVOKE(DECLARE, DEFAULT, FOO_EXPORT)
// will export to call
// EXPORT_TEMPLATE_DECLARE_DEFAULT(FOO_EXPORT, )
// (but with FOO_EXPORT expanded too).
// Default style is to apply the FOO_EXPORT macro at declaration sites.
// The "MSVC hack" style is used when FOO_EXPORT is defined
// as __declspec(dllexport), which MSVC requires to be used at
// definition sites instead.
// EXPORT_TEMPLATE_STYLE is an internal helper macro that identifies which
// export style needs to be used for the provided FOO_EXPORT macro definition.
// "", "__attribute__(...)", and "__declspec(dllimport)" are mapped
// to "DEFAULT"; while "__declspec(dllexport)" is mapped to "MSVC_HACK".
//
// It's implemented with token pasting to transform the __attribute__ and
// __declspec annotations into macro invocations. E.g., if FOO_EXPORT is
// defined as "__declspec(dllimport)", it undergoes the following sequence of
// macro substitutions:
// EXPORT_TEMPLATE_STYLE(FOO_EXPORT, )
// EXPORT_TEMPLATE_STYLE_2(__declspec(dllimport), )
// EXPORT_TEMPLATE_STYLE_3(EXPORT_TEMPLATE_STYLE_MATCH__declspec(dllimport))
// EXPORT_TEMPLATE_STYLE_MATCH__declspec(dllimport)
// EXPORT_TEMPLATE_STYLE_MATCH_DECLSPEC_dllimport
// DEFAULT
// Internal helper macros for EXPORT_TEMPLATE_STYLE.
//
// XXX: C++ reserves all identifiers containing "__" for the implementation,
// but "__attribute__" and "__declspec" already contain "__" and the token-paste
// operator can only add characters; not remove them. To minimize the risk of
// conflict with implementations, we include "foj3FJo5StF0OvIzl7oMxA" (a random
// 128-bit string, encoded in Base64) in the macro name.
// Internal helper macros for EXPORT_TEMPLATE_STYLE.
// Sanity checks.
//
// EXPORT_TEMPLATE_TEST uses the same macro invocation pattern as
// EXPORT_TEMPLATE_DECLARE and EXPORT_TEMPLATE_DEFINE do to check that they're
// working correctly. When they're working correctly, the sequence of macro
// replacements should go something like:
//
// EXPORT_TEMPLATE_TEST(DEFAULT, __declspec(dllimport));
//
// static_assert(EXPORT_TEMPLATE_INVOKE(TEST_DEFAULT,
// EXPORT_TEMPLATE_STYLE(__declspec(dllimport), ),
// __declspec(dllimport)), "__declspec(dllimport)");
//
// static_assert(EXPORT_TEMPLATE_INVOKE(TEST_DEFAULT,
// DEFAULT, __declspec(dllimport)), "__declspec(dllimport)");
//
// static_assert(EXPORT_TEMPLATE_TEST_DEFAULT_DEFAULT(
// __declspec(dllimport)), "__declspec(dllimport)");
//
// static_assert(true, "__declspec(dllimport)");
//
// When they're not working correctly, a syntax error should occur instead.
;
;
;
;