build/docs/preprocessor.rst@97036ab72558 (annotated)
build/docs/preprocessor.rst
Tue, 06 Jan 2015 21:39:09 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Tue, 06 Jan 2015 21:39:09 +0100
- branch
- TOR_BUG_9701
- changeset 8
- 97036ab72558
- permissions
- -rw-r--r--
Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
| michael@0 | 1 | .. _preprocessor: |
| michael@0 | 2 | |
| michael@0 | 3 | ================= |
| michael@0 | 4 | Text Preprocessor |
| michael@0 | 5 | ================= |
| michael@0 | 6 | |
| michael@0 | 7 | The build system contains a text preprocessor similar to the C preprocessor, |
| michael@0 | 8 | meant for processing files which have no built-in preprocessor such as XUL |
| michael@0 | 9 | and JavaScript documents. It is implemented at ``python/mozbuild/mozbuild/preprocessor.py`` and |
| michael@0 | 10 | is typically invoked via :ref:`jar_manifests`. |
| michael@0 | 11 | |
| michael@0 | 12 | While used to preprocess CSS files, the directives are changed to begin with |
| michael@0 | 13 | ``%`` instead of ``#`` to avoid conflict of the id selectors. |
| michael@0 | 14 | |
| michael@0 | 15 | Directives |
| michael@0 | 16 | ========== |
| michael@0 | 17 | |
| michael@0 | 18 | Variable Definition |
| michael@0 | 19 | ------------------- |
| michael@0 | 20 | |
| michael@0 | 21 | define |
| michael@0 | 22 | ^^^^^^ |
| michael@0 | 23 | |
| michael@0 | 24 | :: |
| michael@0 | 25 | |
| michael@0 | 26 | #define variable |
| michael@0 | 27 | #define variable value |
| michael@0 | 28 | |
| michael@0 | 29 | Defines a preprocessor variable. |
| michael@0 | 30 | |
| michael@0 | 31 | Note that, unlike the C preprocessor, instances of this variable later in the |
| michael@0 | 32 | source are not automatically replaced (see #filter). If value is not supplied, |
| michael@0 | 33 | it defaults to ``1``. |
| michael@0 | 34 | |
| michael@0 | 35 | Note that whitespace is significant, so ``"#define foo one"`` and |
| michael@0 | 36 | ``"#define foo one "`` is different (in the second case, ``foo`` is defined to |
| michael@0 | 37 | be a four-character string). |
| michael@0 | 38 | |
| michael@0 | 39 | undef |
| michael@0 | 40 | ^^^^^ |
| michael@0 | 41 | |
| michael@0 | 42 | :: |
| michael@0 | 43 | |
| michael@0 | 44 | #undef variable |
| michael@0 | 45 | |
| michael@0 | 46 | Undefines a preprocessor variable. |
| michael@0 | 47 | |
| michael@0 | 48 | Conditionals |
| michael@0 | 49 | ------------ |
| michael@0 | 50 | |
| michael@0 | 51 | if |
| michael@0 | 52 | ^^ |
| michael@0 | 53 | |
| michael@0 | 54 | :: |
| michael@0 | 55 | |
| michael@0 | 56 | #if variable |
| michael@0 | 57 | #if !variable |
| michael@0 | 58 | #if variable==string |
| michael@0 | 59 | #if variable!=string |
| michael@0 | 60 | |
| michael@0 | 61 | Disables output if the conditional is false. This can be nested to arbitrary |
| michael@0 | 62 | depths. Note that in the equality checks, the variable must come first, and |
| michael@0 | 63 | the comparison operator must not be surrounded by any whitespace. |
| michael@0 | 64 | |
| michael@0 | 65 | else |
| michael@0 | 66 | ^^^^ |
| michael@0 | 67 | |
| michael@0 | 68 | :: |
| michael@0 | 69 | |
| michael@0 | 70 | #else |
| michael@0 | 71 | |
| michael@0 | 72 | Reverses the state of the previous conditional block; for example, if the |
| michael@0 | 73 | last ``#if`` was true (output was enabled), an ``#else`` makes it off |
| michael@0 | 74 | (output gets disabled). |
| michael@0 | 75 | |
| michael@0 | 76 | .. warning:: An ``#else`` is relative to the last conditional block only, |
| michael@0 | 77 | unlike the C preprocessor. |
| michael@0 | 78 | |
| michael@0 | 79 | It does not matter whether any blocks before it were true. This behavior |
| michael@0 | 80 | changed on trunk (Gecko 1.9) on 2006-12-07; see Bug 277122 for details. |
| michael@0 | 81 | |
| michael@0 | 82 | :: |
| michael@0 | 83 | |
| michael@0 | 84 | #if 1 |
| michael@0 | 85 | always included |
| michael@0 | 86 | #elif 1 |
| michael@0 | 87 | never included |
| michael@0 | 88 | #else |
| michael@0 | 89 | always included |
| michael@0 | 90 | #endif |
| michael@0 | 91 | |
| michael@0 | 92 | endif |
| michael@0 | 93 | ^^^^^ |
| michael@0 | 94 | |
| michael@0 | 95 | :: |
| michael@0 | 96 | |
| michael@0 | 97 | #endif |
| michael@0 | 98 | |
| michael@0 | 99 | Ends the conditional block. |
| michael@0 | 100 | |
| michael@0 | 101 | ifdef / ifndef |
| michael@0 | 102 | ^^^^^^^^^^^^^^ |
| michael@0 | 103 | |
| michael@0 | 104 | :: |
| michael@0 | 105 | |
| michael@0 | 106 | #ifdef variable |
| michael@0 | 107 | #ifndef variable |
| michael@0 | 108 | |
| michael@0 | 109 | An ``#if`` conditional that is true only if the preprocessor variable |
| michael@0 | 110 | variable is defined (in the case of ``ifdef``) or not defined (``ifndef``). |
| michael@0 | 111 | |
| michael@0 | 112 | elif / elifdef / elifndef |
| michael@0 | 113 | ^^^^^^^^^^^^^^^^^^^^^^^^^ |
| michael@0 | 114 | |
| michael@0 | 115 | :: |
| michael@0 | 116 | |
| michael@0 | 117 | #elif variable |
| michael@0 | 118 | #elif !variable |
| michael@0 | 119 | #elif variable == string |
| michael@0 | 120 | #elif variable != string |
| michael@0 | 121 | #elifdef variable |
| michael@0 | 122 | #elifndef variable |
| michael@0 | 123 | |
| michael@0 | 124 | A shorthand to mean an ``#else`` combined with the relevant conditional. |
| michael@0 | 125 | The following two blocks are equivalent:: |
| michael@0 | 126 | |
| michael@0 | 127 | #ifdef foo |
| michael@0 | 128 | block 1 |
| michael@0 | 129 | #elifdef bar |
| michael@0 | 130 | block 2 |
| michael@0 | 131 | #endif |
| michael@0 | 132 | |
| michael@0 | 133 | :: |
| michael@0 | 134 | |
| michael@0 | 135 | #ifdef foo |
| michael@0 | 136 | block 1 |
| michael@0 | 137 | #else |
| michael@0 | 138 | #ifdef bar |
| michael@0 | 139 | block 2 |
| michael@0 | 140 | #endif |
| michael@0 | 141 | #endif |
| michael@0 | 142 | |
| michael@0 | 143 | .. warning:: An ``#elif``, ``#elifdef``, or ``#elifndef`` is relative to |
| michael@0 | 144 | the last conditional block only (as well as the condition it implies), |
| michael@0 | 145 | unlike the C preprocessor. It does not matter whether any blocks before |
| michael@0 | 146 | it were true. This behavior changed on trunk (Gecko 1.9) on 2006-12-07. |
| michael@0 | 147 | See Bug 277122 for details. |
| michael@0 | 148 | |
| michael@0 | 149 | File Inclusion |
| michael@0 | 150 | -------------- |
| michael@0 | 151 | |
| michael@0 | 152 | include |
| michael@0 | 153 | ^^^^^^^ |
| michael@0 | 154 | |
| michael@0 | 155 | :: |
| michael@0 | 156 | |
| michael@0 | 157 | #include filename |
| michael@0 | 158 | |
| michael@0 | 159 | The file specified by filename is processed as if the contents was placed |
| michael@0 | 160 | at this position. This also means that preprocessor conditionals can even |
| michael@0 | 161 | be started in one file and ended in another (but is highly discouraged). |
| michael@0 | 162 | There is no limit on depth of inclusion, or repeated inclusion of the same |
| michael@0 | 163 | file, or self inclusion; thus, care should be taken to avoid infinite loops. |
| michael@0 | 164 | |
| michael@0 | 165 | includesubst |
| michael@0 | 166 | ^^^^^^^^^^^^ |
| michael@0 | 167 | |
| michael@0 | 168 | :: |
| michael@0 | 169 | |
| michael@0 | 170 | #includesubst @variable@filename |
| michael@0 | 171 | |
| michael@0 | 172 | Same as a ``#include`` except that all instances of variable in the included |
| michael@0 | 173 | file is also expanded as in ``#filter`` substitution |
| michael@0 | 174 | |
| michael@0 | 175 | expand |
| michael@0 | 176 | ^^^^^^ |
| michael@0 | 177 | |
| michael@0 | 178 | :: |
| michael@0 | 179 | |
| michael@0 | 180 | #expand string |
| michael@0 | 181 | |
| michael@0 | 182 | All variables wrapped in ``__`` are replaced with their value, for this line |
| michael@0 | 183 | only. If the variable is not defined, it expands to an empty string. For |
| michael@0 | 184 | example, if ``foo`` has the value ``bar``, and ``baz`` is not defined, then:: |
| michael@0 | 185 | |
| michael@0 | 186 | #expand This <__foo__> <__baz__> gets expanded |
| michael@0 | 187 | |
| michael@0 | 188 | Is expanded to:: |
| michael@0 | 189 | |
| michael@0 | 190 | This <bar> <> gets expanded |
| michael@0 | 191 | |
| michael@0 | 192 | filter / unfilter |
| michael@0 | 193 | ^^^^^^^^^^^^^^^^^ |
| michael@0 | 194 | |
| michael@0 | 195 | :: |
| michael@0 | 196 | |
| michael@0 | 197 | #filter filter1 filter2 ... filterN |
| michael@0 | 198 | #unfilter filter1 filter2 ... filterN |
| michael@0 | 199 | |
| michael@0 | 200 | ``#filter`` turns on the given filter. |
| michael@0 | 201 | |
| michael@0 | 202 | Filters are run in alphabetical order on a per-line basis. |
| michael@0 | 203 | |
| michael@0 | 204 | ``#unfilter`` turns off the given filter. Available filters are: |
| michael@0 | 205 | |
| michael@0 | 206 | emptyLines |
| michael@0 | 207 | strips blank lines from the output |
| michael@0 | 208 | slashslash |
| michael@0 | 209 | strips everything from the first two consecutive slash (``/``) |
| michael@0 | 210 | characters until the end of the line |
| michael@0 | 211 | spaces |
| michael@0 | 212 | collapses consecutive sequences of spaces into a single space, |
| michael@0 | 213 | and strips leading and trailing spaces |
| michael@0 | 214 | substitution |
| michael@0 | 215 | all variables wrapped in @ are replaced with their value. If the |
| michael@0 | 216 | variable is not defined, it is a fatal error. Similar to ``#expand`` |
| michael@0 | 217 | and ``#filter`` |
| michael@0 | 218 | attemptSubstitution |
| michael@0 | 219 | all variables wrapped in ``@`` are replaced with their value, or an |
| michael@0 | 220 | empty string if the variable is not defined. Similar to ``#expand``. |
| michael@0 | 221 | |
| michael@0 | 222 | literal |
| michael@0 | 223 | ^^^^^^^ |
| michael@0 | 224 | |
| michael@0 | 225 | :: |
| michael@0 | 226 | |
| michael@0 | 227 | #literal string |
| michael@0 | 228 | |
| michael@0 | 229 | Output the string (i.e. the rest of the line) literally, with no other fixups. |
| michael@0 | 230 | This is useful to output lines starting with ``#``, or to temporarily |
| michael@0 | 231 | disable filters. |
| michael@0 | 232 | |
| michael@0 | 233 | Other |
| michael@0 | 234 | ----- |
| michael@0 | 235 | |
| michael@0 | 236 | #error |
| michael@0 | 237 | ^^^^^^ |
| michael@0 | 238 | |
| michael@0 | 239 | :: |
| michael@0 | 240 | |
| michael@0 | 241 | #error string |
| michael@0 | 242 | |
| michael@0 | 243 | Cause a fatal error at this point, with the error message being the |
| michael@0 | 244 | given string. |
