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| 7 In 1999, SGI added “<span class="quote">concept checkers</span>” to their | |
| 8 implementation of the STL: code which checked the template | |
| 9 parameters of instantiated pieces of the STL, in order to insure | |
| 10 that the parameters being used met the requirements of the | |
| 11 standard. For example, the Standard requires that types passed as | |
| 12 template parameters to <code class="classname">vector</code> be | |
| 13 "Assignable" (which means what you think it means). The | |
| 14 checking was done during compilation, and none of the code was | |
| 15 executed at runtime. | |
| 16 </p><p> | |
| 17 Unfortunately, the size of the compiler files grew significantly | |
| 18 as a result. The checking code itself was cumbersome. And bugs | |
| 19 were found in it on more than one occasion. | |
| 20 </p><p> | |
| 21 The primary author of the checking code, Jeremy Siek, had already | |
| 22 started work on a replacement implementation. The new code has been | |
| 23 formally reviewed and accepted into | |
| 24 <a class="ulink" href="http://www.boost.org/libs/concept_check/concept_check.
htm" target="_top">the | |
| 25 Boost libraries</a>, and we are pleased to incorporate it into the | |
| 26 GNU C++ library. | |
| 27 </p><p> | |
| 28 The new version imposes a much smaller space overhead on the generated | |
| 29 object file. The checks are also cleaner and easier to read and | |
| 30 understand. | |
| 31 </p><p> | |
| 32 They are off by default for all versions of GCC. | |
| 33 They can be enabled at configure time with | |
| 34 <a class="ulink" href="../configopts.html" target="_top"><code class="literal
">--enable-concept-checks</code></a>. | |
| 35 You can enable them on a per-translation-unit basis with | |
| 36 <code class="literal">-D_GLIBCXX_CONCEPT_CHECKS</code>. | |
| 37 </p><p> | |
| 38 Please note that the upcoming C++ standard has first-class | |
| 39 support for template parameter constraints based on concepts in the core | |
| 40 language. This will obviate the need for the library-simulated concept | |
| 41 checking described above. | |
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Chromium Code Reviews
Issue 3050029:
[gcc] GCC 4.5.0=>4.5.1 (Closed)
Base URL: ssh://git@gitrw.chromium.org:9222/nacl-toolchain.git