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Author SHA1 Message Date
c29ae51d80 Create branches/filesystem-v3 for v2 removal
[SVN r77385]
2012-03-18 20:54:17 +00:00
e910489e16 Add BOOST_STATIC_ASSERT_MSG
[SVN r68584]
2011-01-31 15:03:41 +00:00
3 changed files with 37 additions and 7 deletions

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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

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@ -17,6 +17,12 @@
#include <boost/config.hpp>
#include <boost/detail/workaround.hpp>
#ifndef BOOST_NO_STATIC_ASSERT
# define BOOST_STATIC_ASSERT_MSG( B, Msg ) static_assert(B, Msg)
#else
# define BOOST_STATIC_ASSERT_MSG( B, Msg ) BOOST_STATIC_ASSERT( B )
#endif
#ifdef __BORLANDC__
//
// workaround for buggy integral-constant expression support:

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@ -16,12 +16,16 @@
// Namespace scope
BOOST_STATIC_ASSERT(sizeof(int) >= sizeof(short));
BOOST_STATIC_ASSERT(sizeof(char) == 1);
BOOST_STATIC_ASSERT_MSG(sizeof(int) >= sizeof(short), "msg1");
BOOST_STATIC_ASSERT_MSG(sizeof(char) == 1, "msg2");
// Function (block) scope
void f()
{
BOOST_STATIC_ASSERT(sizeof(int) >= sizeof(short));
BOOST_STATIC_ASSERT(sizeof(char) == 1);
BOOST_STATIC_ASSERT_MSG(sizeof(int) >= sizeof(short), "msg3");
BOOST_STATIC_ASSERT_MSG(sizeof(char) == 1, "msg4");
}
struct Bob
@ -29,6 +33,8 @@ struct Bob
private: // can be in private, to avoid namespace pollution
BOOST_STATIC_ASSERT(sizeof(int) >= sizeof(short));
BOOST_STATIC_ASSERT(sizeof(char) == 1);
BOOST_STATIC_ASSERT_MSG(sizeof(int) >= sizeof(short), "msg5");
BOOST_STATIC_ASSERT_MSG(sizeof(char) == 1, "msg6");
public:
// Member function scope: provides access to member variables
@ -36,9 +42,11 @@ struct Bob
char c;
int f()
{
#ifndef _MSC_VER // broken sizeof in VC6
#if defined(_MSC_VER) && _MSC_VER < 1300 // broken sizeof in VC6
BOOST_STATIC_ASSERT(sizeof(x) >= sizeof(short));
BOOST_STATIC_ASSERT(sizeof(c) == 1);
BOOST_STATIC_ASSERT_MSG(sizeof(x) >= sizeof(short), "msg7");
BOOST_STATIC_ASSERT_MSG(sizeof(c) == 1, "msg8");
#endif
return x;
}
@ -52,6 +60,7 @@ struct Bill
{
private: // can be in private, to avoid namespace pollution
BOOST_STATIC_ASSERT(sizeof(Int) > sizeof(char));
BOOST_STATIC_ASSERT_MSG(sizeof(Int) > sizeof(char), "msg9");
public:
// Template member function scope: provides access to member variables
@ -62,10 +71,12 @@ struct Bill
{
BOOST_STATIC_ASSERT(sizeof(Int) == sizeof(Int2));
BOOST_STATIC_ASSERT(sizeof(Char) == sizeof(Char2));
BOOST_STATIC_ASSERT_MSG(sizeof(Int) == sizeof(Int2), "msg10");
BOOST_STATIC_ASSERT_MSG(sizeof(Char) == sizeof(Char2), "msg11");
}
};
void test_Bill() // BOOST_CT_ASSERTs are not triggerred until instantiated
void test_Bill() // BOOST_STATIC_ASSERTs are not triggerred until instantiated
{
Bill<int, char> z;
//Bill<int, int> bad; // will not compile