Also known as concept checking.
In 1999, SGI added concept checkers to their implementation
of the STL: code which checked the template parameters of
instantiated pieces of the STL, in order to insure that the parameters
being used met the requirements of the standard. For example,
the Standard requires that types passed as template parameters to
vector be “Assignable” (which means what you think
it means). The checking was done during compilation, and none of
the code was executed at runtime.
Unfortunately, the size of the compiler files grew significantly as a result. The checking code itself was cumbersome. And bugs were found in it on more than one occasion.
The primary author of the checking code, Jeremy Siek, had already started work on a replacement implementation. The new code has been formally reviewed and accepted into the Boost libraries, and we are pleased to incorporate it into the GNU C++ library.
The new version imposes a much smaller space overhead on the generated object file. The checks are also cleaner and easier to read and understand.
They are off by default for all versions of GCC from 3.0 to 3.4 (the
latest release at the time of writing).
They can be enabled at configure time with
--enable-concept-checks.
You can enable them on a per-translation-unit basis with
#define _GLIBCXX_CONCEPT_CHECKS for GCC 3.4 and higher
(or with #define _GLIBCPP_CONCEPT_CHECKS for versions
3.1, 3.2 and 3.3).
Please note that the upcoming C++ standard has first-class support for template parameter constraints based on concepts in the core language. This will obviate the need for the library-simulated concept checking described above.
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Please note that the concept checks only validate the requirements
of the old C++03 standard. C++11 was expected to have first-class
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language. This would have obviated the need for the library-simulated concept
checking described above, but was not part of C++11.
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@import GCC 5.4.0 release. there's not a lot of new info though at
least these 135 (!) GCC PRs have been fixed by the update:
68730 69714 67550 70209 71254 70839 69737 70067 67355 67172 69239
65779 69546 70272 70421 65985 67339 67411 68309 68585 68679 68890
68949 69009 70139 70494 68162 69135 70306 68965 70297 70635 66786
69098 70347 69719 70526 70941 69400 69577 69447 65689 65886 65932
66655 68269 68789 69614 69648 69666 69764 69794 70044 70052 65726
68910 64289 68671 68835 69669 70329 71204 69355 67364 68049 68998
69323 69743 69995 69146 68651 67755 67484 68790 68907 69099 69496
69509 69516 70393 69222 69703 69939 70609 71004 71005 71036 71037
71038 68636 69013 69606 70115 70333 70430 60290 70356 69305 70024
67781 69414 69140 70510 60164 66635 67896 68106 68298 68449 68779
68921 68986 69037 69147 69194 69366 69399 69705 69917 69969 70613
71317 69268 70269 69032 65702 69219 69484 65996 66680 68283 69603
70350 67451 61397
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#define
_GLIBCXX_CONCEPT_CHECKS for GCC 3.4 and higher
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@Sync with HEAD
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