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14d7100d | 1 | .\" -*-nroff-*- |
2 | .TH macros 3 "13 December 2003" "Straylight/Edgeware" "mLib utilities library" | |
3 | .SH NAME | |
4 | macros \- useful macros | |
5 | .\" @N | |
3832000d MW |
6 | .\" @STR |
7 | .\" @GLUE | |
f50c1365 | 8 | .\" @STATIC_ASSERT |
3832000d MW |
9 | .\" @DISCARD |
10 | .\" @IGNORE | |
11 | .\" @DEPRECATED | |
12 | .\" @EXECL_LIKE | |
13 | .\" @IGNORABLE | |
14 | .\" @NORETURN | |
15 | .\" @PRINTF_LIKE | |
16 | .\" @SCANF_LIKE | |
17 | .\" @MUFFLE_WARNINGS_DECL | |
18 | .\" @MUFFLE_WARNINGS_EXPR | |
19 | .\" @MUFFLE_WARNINGS_STMT | |
3832000d | 20 | .\" @GCC_WARNING |
14d7100d | 21 | .SH SYNOPSIS |
22 | .nf | |
23 | .B "#include <mLib/macros.h>" | |
24 | ||
25 | .BI "size_t N(" array ");" | |
3832000d MW |
26 | .BI "STR(" tokens\fR... ")" |
27 | .BI "GLUE(" tokens\fR... ", " tokens\fR... ")" | |
f50c1365 | 28 | .BI "STATIC_ASSERT(" cond ", " msg ");" |
3832000d MW |
29 | |
30 | .BI "void DISCARD(" scalar ");" | |
31 | .BI "void IGNORE(" variable ");" | |
32 | ||
33 | .BI "DEPRECATED(" msg ")" | |
34 | .BI "EXECL_LIKE(" ntrail ")" | |
35 | .BI "IGNORABLE" | |
36 | .BI "NORETURN" | |
37 | .BI "PRINTF_LIKE(" fmt-index ", " arg-index ")" | |
38 | .BI "SCANF_LIKE(" fmt-index ", " arg-index ")" | |
39 | ||
40 | .BI "MUFFLE_WARNINGS_DECL(" warns ", " decls ")" | |
41 | .BI "MUFFLE_WARNINGS_EXPR(" warns ", " expr ")" | |
42 | .BI "MUFFLE_WARNINGS_STMT(" warns ", " stmt ")" | |
43 | ||
3832000d | 44 | .BI "GCC_WARNING(" option ")" |
c418910f | 45 | .BI "CLANG_WARNING(" option ")" |
14d7100d | 46 | .fi |
47 | .SH DESCRIPTION | |
3832000d | 48 | .SS Utilities |
14d7100d | 49 | The |
50 | .B N | |
51 | macro returns the number of elements in the named | |
52 | .IR array . | |
3832000d MW |
53 | .PP |
54 | The | |
55 | .B STR | |
56 | macro expands to a string literal containing the result of expanding its | |
57 | argument | |
58 | .IR tokens . | |
59 | .PP | |
60 | The | |
61 | .B GLUE | |
62 | macro expands to a single token, which is the result of gluing together | |
63 | the tokens resulting from expanding its argument token lists. Each of | |
64 | the argument token lists must expand to a single preprocessing token, | |
65 | and the result of gluing these tokens together must be valid | |
66 | preprocessing token. | |
67 | .PP | |
68 | The | |
f50c1365 MW |
69 | .B STATIC_ASSERT |
70 | causes compilation to fail if the integer constant expression | |
71 | .I cond | |
72 | evaluates to zero. This macro uses the C11 | |
73 | .B static_assert | |
74 | declaration if available, and the | |
75 | .I msg | |
76 | will be reported in the compiler's diagnostic messsage; otherwise, the macro | |
77 | falls back to a somewhat ugly hack which currently ignores the | |
78 | .IR msg . | |
79 | .PP | |
80 | The | |
3832000d MW |
81 | .B DISCARD |
82 | macro discards its argument, which must be of some scalar type. This | |
83 | can be useful in muffling warnings about ignoring return codes in cases | |
84 | where you really don't care. | |
85 | .PP | |
86 | The | |
87 | .B IGNORE | |
88 | macro ignores its argument, which may be an expression of any type. | |
89 | This can be useful in muffling warnings about unused variables. | |
90 | .SS Annotations | |
91 | The following annotations can be attached to function declarations and | |
92 | definitions, as part of the declaration specifiers. (Other positions | |
93 | may also work, depending on your compiler, but don't bet on it.) They | |
94 | might not have any effect, depending on your specific compiler. | |
95 | Currently only GCC is well supported, but exactly which features are | |
96 | available depend on the compiler version. | |
97 | .PP | |
98 | Using a function or variable marked as | |
99 | .B DEPRECATED | |
100 | may provoke a compiler warning; this warning may (depending on your | |
101 | compiler version) include the given | |
102 | .IR msg . | |
103 | .PP | |
104 | A variadic function marked as | |
105 | .B EXECL_LIKE | |
106 | must be called with a null pointer (i.e., an integer constant | |
107 | expression with value 0, cast to | |
108 | .BR "void *") | |
109 | in the variadic part of its argument list, followed by | |
110 | .I ntrail | |
111 | further arguments. Typically, | |
112 | .I ntrail | |
113 | is zero. Compilers may warn about misuse of such functions. | |
114 | .PP | |
115 | A function or variable marked as | |
116 | .B IGNORABLE | |
117 | need not be used. This may muffle warnings about leaving the marked | |
118 | definition unused. | |
119 | .PP | |
120 | A function marked as | |
121 | .B NORETURN | |
122 | must not return. It must have return type | |
123 | .BR void . | |
124 | This may be useful in muffling warnings about uninitialized variables, | |
125 | for example. | |
126 | .PP | |
127 | A variadic function marked as | |
128 | .B PRINTF_LIKE | |
129 | takes a | |
130 | .BR printf (3)-style | |
131 | format argument (in position | |
132 | .IR fmt-index , | |
133 | counting from 1) and a variable-length list of arguments to be formatted | |
134 | (starting from position | |
135 | .IR arg-index ). | |
136 | Compilers may warn about misuse of such functions. | |
137 | .PP | |
138 | A variadic function marked as | |
139 | .B SCANF_LIKE | |
140 | takes a | |
141 | .BR scanf (3)-style | |
142 | format argument (in position | |
143 | .IR fmt-index , | |
144 | counting from 1) and a variable-length list of arguments to be formatted | |
145 | (starting from position | |
146 | .IR arg-index ). | |
147 | Compilers may warn about misuse of such functions. | |
148 | .SS Muffling warnings | |
149 | Some compilers allow you to muffle warnings in particular pieces of | |
150 | code. These macros provide a compiler-neutral interface to such | |
151 | facilities. Each macro takes an argument | |
152 | .IR warns , | |
153 | which is a sequence of calls to | |
154 | .IB compiler _WARNING | |
155 | macros listing the warnings to be muffled. The list may contain | |
156 | warnings for several different compilers. The other argument is a | |
157 | .I body | |
158 | consisting of declarations (in the case of | |
159 | .BR MUFFLE_WARNINGS_DECL ), | |
160 | an expression (for | |
161 | .BR MUFFLE_WARNINGS_EXPR ), | |
162 | or a statement (for | |
163 | .BR MUFFLE_WARNINGS_STMT ). | |
164 | .SS GCC-specific features | |
165 | The | |
166 | .B GCC_VERSION_P | |
167 | macro returns a nonzero value if the compiler is at least version | |
168 | .IB maj . min | |
169 | of GCC, and zero otherwise. It's useful in preprocessor conditions. | |
170 | .PP | |
171 | The | |
172 | .B GCC_WARNING | |
173 | macro is intended to be used in | |
174 | .I warns | |
175 | lists (see above). It takes a string-literal argument | |
176 | .I option | |
177 | naming a GCC warning option, e.g., | |
178 | .BR """\-Wdiv-by-zero""" . | |
c418910f MW |
179 | .PP |
180 | The | |
181 | .B CLANG_WARNING | |
182 | is similar, except that it works with the Clang compiler. | |
33e3ac90 MW |
183 | .PP |
184 | Note that including | |
185 | .B <mLib/macros.h> | |
186 | also defines the compiler-test macros in | |
187 | .BR <mLib/compiler.h>; | |
188 | see | |
189 | .BR compiler (3). | |
14d7100d | 190 | .SH "SEE ALSO" |
33e3ac90 MW |
191 | .BR mLib (3), |
192 | .BR compiler (3). | |
14d7100d | 193 | .SH "AUTHOR" |
9b5ac6ff | 194 | Mark Wooding, <mdw@distorted.org.uk> |