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Added notes about mixing objects compiled with different RTTI falgs

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Antony Polukhin
2013-10-22 17:00:03 +04:00
parent 6d1d4b62f3
commit 5445bbc85f
2 changed files with 21 additions and 0 deletions
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3
boost/type_index/type_index_minimal.hpp
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@ -19,6 +19,9 @@
///
/// It includes only the minamally required headers and does the `typedef template_index type_index;`
/// when RTTI is disabled.
///
/// Define the BOOST_TYPE_INDEX_FORCE_NORTTI_COMPATIBILITY macro if you are mixing objects
/// compiled with different RTTI flags.
#include <boost/config.hpp>

18
libs/type_index/doc/type_index.qbk
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@ -119,3 +119,21 @@ Consider the following example:
With `BOOST_TYPE_INDEX_CTTI_BEGIN_SKIP` and `BOOST_TYPE_INDEX_CTTI_END_SKIP` set to `0`, `boost::detail::ctti<int>::n()` returns "const char *__cdecl boost::detail::ctti<int>::n(void)". Then you shall set `BOOST_TYPE_INDEX_CTTI_BEGIN_SKIP` to `sizeof("const char *__cdecl boost::detail::ctti<") - 1` and `BOOST_TYPE_INDEX_CTTI_END_SKIP` to `sizeof(">::n(void)") - 1`
[endsect]
[section Mixing sources with RTTI on and RTTI off]
Linking a binary from source files that were compiled with different RTTI flags is not a very good idea and may lead to a lot of surprises. However if there is a very strong need TypeIndex library provides a solution for mixing sources: just define `BOOST_TYPE_INDEX_FORCE_NORTTI_COMPATIBILITY` macro. This would lead to usage of `boost::template_index` instead of `boost::type_index` class.
[note Do not forget to rebuild *all* the projects with `BOOST_TYPE_INDEX_FORCE_NORTTI_COMPATIBILITY` macro defined ]
You must know that linking RTTI on and RTTI off binaries may succeed even without defining the `BOOST_TYPE_INDEX_FORCE_NORTTI_COMPATIBILITY` macro, but that does not mean that you'll get a working binary. Such actions may break the One Definition Rule. Take a look at the table below, that shows how the `boost::type_index get_integer();` function will look like with different RTTI flags:
[table:diffs
[[RTTI on] [RTTI off]]
[[`boost::type_index get_integer();`] [`boost::template_index get_integer();`]]
]
Such differences are usually not detected by linker and lead to errors at runtime.
[endsect]