1 | |
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2 | [/ Copyright 2005-2006 Daniel James. |
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3 | / Distributed under the Boost Software License, Version 1.0. (See accompanying |
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4 | / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) ] |
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5 | |
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6 | [section:disable Disabling The Extensions] |
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7 | |
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8 | While [classref boost::hash]'s extensions are generally useful, you might want |
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9 | to turn them of in order to check that your code will work with other |
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10 | implementations of TR1. To do this define the macro `BOOST_HASH_NO_EXTENSIONS`. |
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11 | When this macro is defined, only the specialisations detailed |
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12 | in TR1 will be declared. But, if you later undefine the macro and include |
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13 | <[headerref boost/functional/hash.hpp]> then the non-specialised form will be defined |
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14 | - activating the extensions. |
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15 | |
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16 | It is strongly recommended that you never undefine the macro - and only define |
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17 | it so that it applies to the complete translation unit, either by defining it |
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18 | at the beginning of the main source file or, preferably, by using a compiler |
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19 | switch or preference. And you really should never define it in header files. |
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20 | |
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21 | If you are writing a library which has code in the header which requires the |
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22 | extensions, then the best action is to tell users not to define the macro. |
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23 | Their code won't ['require] the macro. |
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24 | |
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25 | Translation units that are compiled with the macro defined will link with units |
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26 | that were compiled without it. This feature has been designed to avoid ODR |
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27 | violations. |
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28 | |
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29 | [endsect] |
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