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| <h3 class="section">3.1 Preprocessing</h3> |
| |
| <p><a name="index-preprocessing-114"></a>The <samp><span class="command">as</span></samp> internal preprocessor: |
| |
| <a name="index-whitespace_002c-removed-by-preprocessor-115"></a> |
| <ul><li>adjusts and removes extra whitespace. It leaves one space or tab before |
| the keywords on a line, and turns any other whitespace on the line into |
| a single space. |
| |
| <p><a name="index-comments_002c-removed-by-preprocessor-116"></a><li>removes all comments, replacing them with a single space, or an |
| appropriate number of newlines. |
| |
| <p><a name="index-constants_002c-converted-by-preprocessor-117"></a><li>converts character constants into the appropriate numeric values. |
| </ul> |
| |
| <p>It does not do macro processing, include file handling, or |
| anything else you may get from your C compiler's preprocessor. You can |
| do include file processing with the <code>.include</code> directive |
| (see <a href="Include.html#Include"><code>.include</code></a>). You can use the <span class="sc">gnu</span> C compiler driver |
| to get other “CPP” style preprocessing by giving the input file a |
| ‘<samp><span class="samp">.S</span></samp>’ suffix. See <a href="../gcc/Overall-Options.html#Overall-Options">Options Controlling the Kind of Output</a>. |
| |
| <p>Excess whitespace, comments, and character constants |
| cannot be used in the portions of the input text that are not |
| preprocessed. |
| |
| <p><a name="index-turning-preprocessing-on-and-off-118"></a><a name="index-preprocessing_002c-turning-on-and-off-119"></a><a name="index-g_t_0023NO_005fAPP-120"></a><a name="index-g_t_0023APP-121"></a>If the first line of an input file is <code>#NO_APP</code> or if you use the |
| ‘<samp><span class="samp">-f</span></samp>’ option, whitespace and comments are not removed from the input file. |
| Within an input file, you can ask for whitespace and comment removal in |
| specific portions of the by putting a line that says <code>#APP</code> before the |
| text that may contain whitespace or comments, and putting a line that says |
| <code>#NO_APP</code> after this text. This feature is mainly intend to support |
| <code>asm</code> statements in compilers whose output is otherwise free of comments |
| and whitespace. |
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