| 1 | .\" -*-nroff-*- |
| 2 | .TH macros 3 "13 December 2003" "Straylight/Edgeware" "mLib utilities library" |
| 3 | .SH NAME |
| 4 | macros \- useful macros |
| 5 | .\" @N |
| 6 | .\" @STR |
| 7 | .\" @GLUE |
| 8 | .\" @STATIC_ASSERT |
| 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 |
| 20 | .\" @GCC_WARNING |
| 21 | .SH SYNOPSIS |
| 22 | .nf |
| 23 | .B "#include <mLib/macros.h>" |
| 24 | |
| 25 | .BI "size_t N(" array ");" |
| 26 | .BI "STR(" tokens\fR... ")" |
| 27 | .BI "GLUE(" tokens\fR... ", " tokens\fR... ")" |
| 28 | .BI "STATIC_ASSERT(" cond ", " msg ");" |
| 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 | |
| 44 | .BI "GCC_WARNING(" option ")" |
| 45 | .BI "CLANG_WARNING(" option ")" |
| 46 | .fi |
| 47 | .SH DESCRIPTION |
| 48 | .SS Utilities |
| 49 | The |
| 50 | .B N |
| 51 | macro returns the number of elements in the named |
| 52 | .IR array . |
| 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 |
| 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 |
| 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""" . |
| 179 | .PP |
| 180 | The |
| 181 | .B CLANG_WARNING |
| 182 | is similar, except that it works with the Clang compiler. |
| 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). |
| 190 | .SH "SEE ALSO" |
| 191 | .BR mLib (3), |
| 192 | .BR compiler (3). |
| 193 | .SH "AUTHOR" |
| 194 | Mark Wooding, <mdw@distorted.org.uk> |