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[SVN r71486]
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John Maddock
2011-04-25 17:27:05 +00:00
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doc/static_assert.qbk
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@ -21,15 +21,28 @@ printer friendly PDF format].
[section:intro Overview and Tutorial]
The header `<boost/static_assert.hpp>` supplies a single macro `BOOST_STATIC_ASSERT(x)`,
which generates a compile time error message if the integral-constant-expression `x`
is not true. In other words it is the compile time equivalent of the assert macro;
The header `<boost/static_assert.hpp>` supplies two macros:
BOOST_STATIC_ASSERT(x)
BOOST_STATIC_ASSERT_MSG(x, msg)
Both generate a compile time error message if the integral-constant-expression `x`
is not true. In other words, they are the compile time equivalent of the assert macro;
this is sometimes known as a "compile-time-assertion", but will be called a
"static assertion" throughout these docs. Note that if the condition is `true`,
then the macro will generate neither code nor data - and the macro can also
then the macros will generate neither code nor data - and the macros can also
be used at either namespace, class or function scope. When used in a template,
the static assertion will be evaluated at the time the template is instantiated;
this is particularly useful for validating template parameters.
this is particularly useful for validating template parameters.
If the C++0x `static_assert` feature is available, both macros will use it.
For `BOOST_STATIC_ASSERT(x)`, the error message with be a stringized version of `x`.
For `BOOST_STATIC_ASSERT_MSG(x, msg)`, the error message will be the `msg` string.
If the C++0x `static_assert` feature is not available, `BOOST_STATIC_ASSERT_MSG(x, msg)`
will be treated as `BOOST_STATIC_ASSERT(x)`.
The material that follows assumes the C++0x `static_assert` feature is not available.
One of the aims of `BOOST_STATIC_ASSERT` is to generate readable error messages.
These immediately tell the user that a library is being used in a manner that