forked from boostorg/static_assert
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e910489e16 |
@ -21,15 +21,28 @@ printer friendly PDF format].
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[section:intro Overview and Tutorial]
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The header `<boost/static_assert.hpp>` supplies a single macro `BOOST_STATIC_ASSERT(x)`,
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which generates a compile time error message if the integral-constant-expression `x`
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is not true. In other words it is the compile time equivalent of the assert macro;
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The header `<boost/static_assert.hpp>` supplies two macros:
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BOOST_STATIC_ASSERT(x)
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BOOST_STATIC_ASSERT_MSG(x, msg)
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Both generate a compile time error message if the integral-constant-expression `x`
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is not true. In other words, they are the compile time equivalent of the assert macro;
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this is sometimes known as a "compile-time-assertion", but will be called a
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"static assertion" throughout these docs. Note that if the condition is `true`,
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then the macro will generate neither code nor data - and the macro can also
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then the macros will generate neither code nor data - and the macros can also
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be used at either namespace, class or function scope. When used in a template,
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the static assertion will be evaluated at the time the template is instantiated;
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this is particularly useful for validating template parameters.
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this is particularly useful for validating template parameters.
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If the C++0x `static_assert` feature is available, both macros will use it.
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For `BOOST_STATIC_ASSERT(x)`, the error message with be a stringized version of `x`.
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For `BOOST_STATIC_ASSERT_MSG(x, msg)`, the error message will be the `msg` string.
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If the C++0x `static_assert` feature is not available, `BOOST_STATIC_ASSERT_MSG(x, msg)`
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will be treated as `BOOST_STATIC_ASSERT(x)`.
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The material that follows assumes the C++0x `static_assert` feature is not available.
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One of the aims of `BOOST_STATIC_ASSERT` is to generate readable error messages.
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These immediately tell the user that a library is being used in a manner that
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@ -17,6 +17,12 @@
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#include <boost/config.hpp>
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#include <boost/detail/workaround.hpp>
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#ifndef BOOST_NO_STATIC_ASSERT
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# define BOOST_STATIC_ASSERT_MSG( B, Msg ) static_assert(B, Msg)
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#else
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# define BOOST_STATIC_ASSERT_MSG( B, Msg ) BOOST_STATIC_ASSERT( B )
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#endif
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#ifdef __BORLANDC__
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//
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// workaround for buggy integral-constant expression support:
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@ -16,12 +16,16 @@
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// Namespace scope
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BOOST_STATIC_ASSERT(sizeof(int) >= sizeof(short));
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BOOST_STATIC_ASSERT(sizeof(char) == 1);
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BOOST_STATIC_ASSERT_MSG(sizeof(int) >= sizeof(short), "msg1");
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BOOST_STATIC_ASSERT_MSG(sizeof(char) == 1, "msg2");
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// Function (block) scope
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void f()
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{
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BOOST_STATIC_ASSERT(sizeof(int) >= sizeof(short));
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BOOST_STATIC_ASSERT(sizeof(char) == 1);
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BOOST_STATIC_ASSERT_MSG(sizeof(int) >= sizeof(short), "msg3");
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BOOST_STATIC_ASSERT_MSG(sizeof(char) == 1, "msg4");
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}
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struct Bob
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@ -29,6 +33,8 @@ struct Bob
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private: // can be in private, to avoid namespace pollution
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BOOST_STATIC_ASSERT(sizeof(int) >= sizeof(short));
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BOOST_STATIC_ASSERT(sizeof(char) == 1);
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BOOST_STATIC_ASSERT_MSG(sizeof(int) >= sizeof(short), "msg5");
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BOOST_STATIC_ASSERT_MSG(sizeof(char) == 1, "msg6");
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public:
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// Member function scope: provides access to member variables
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@ -36,9 +42,11 @@ struct Bob
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char c;
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int f()
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{
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#ifndef _MSC_VER // broken sizeof in VC6
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#if defined(_MSC_VER) && _MSC_VER < 1300 // broken sizeof in VC6
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BOOST_STATIC_ASSERT(sizeof(x) >= sizeof(short));
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BOOST_STATIC_ASSERT(sizeof(c) == 1);
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BOOST_STATIC_ASSERT_MSG(sizeof(x) >= sizeof(short), "msg7");
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BOOST_STATIC_ASSERT_MSG(sizeof(c) == 1, "msg8");
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#endif
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return x;
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}
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@ -52,6 +60,7 @@ struct Bill
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{
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private: // can be in private, to avoid namespace pollution
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BOOST_STATIC_ASSERT(sizeof(Int) > sizeof(char));
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BOOST_STATIC_ASSERT_MSG(sizeof(Int) > sizeof(char), "msg9");
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public:
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// Template member function scope: provides access to member variables
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@ -62,10 +71,12 @@ struct Bill
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{
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BOOST_STATIC_ASSERT(sizeof(Int) == sizeof(Int2));
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BOOST_STATIC_ASSERT(sizeof(Char) == sizeof(Char2));
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BOOST_STATIC_ASSERT_MSG(sizeof(Int) == sizeof(Int2), "msg10");
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BOOST_STATIC_ASSERT_MSG(sizeof(Char) == sizeof(Char2), "msg11");
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}
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};
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void test_Bill() // BOOST_CT_ASSERTs are not triggerred until instantiated
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void test_Bill() // BOOST_STATIC_ASSERTs are not triggerred until instantiated
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{
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Bill<int, char> z;
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//Bill<int, int> bad; // will not compile
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