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|---|---|---|
| 7c673cae FG |
1 | .. Macros/Asserts//BOOST_MPL_ASSERT_MSG |
| 2 | ||
| 3 | BOOST_MPL_ASSERT_MSG | |
| 4 | ==================== | |
| 5 | ||
| 6 | Synopsis | |
| 7 | -------- | |
| 8 | ||
| 9 | .. parsed-literal:: | |
| 10 | ||
| 11 | #define BOOST_MPL_ASSERT_MSG( condition, message, types ) \\ | |
| 12 | |unspecified-token-seq| \\ | |
| 13 | /\*\*/ | |
| 14 | ||
| 15 | ||
| 16 | Description | |
| 17 | ----------- | |
| 18 | ||
| 19 | Generates a compilation error with an embedded custom message when the condition | |
| 20 | doesn't hold. | |
| 21 | ||
| 22 | ||
| 23 | Header | |
| 24 | ------ | |
| 25 | ||
| 26 | .. parsed-literal:: | |
| 27 | ||
| 28 | #include <boost/mpl/assert.hpp> | |
| 29 | ||
| 30 | ||
| 31 | Parameters | |
| 32 | ---------- | |
| 33 | ||
| 34 | +---------------+-----------------------------------+-----------------------------------------------+ | |
| 35 | | Parameter | Requirement | Description | | |
| 36 | +===============+===================================+===============================================+ | |
| 37 | | ``condition`` | An integral constant expression | A condition to be asserted. | | |
| 38 | +---------------+-----------------------------------+-----------------------------------------------+ | |
| 39 | | ``message`` | A legal identifier token | A custom message in a form of a legal C++ | | |
| 40 | | | | identifier token. | | |
| 41 | +---------------+-----------------------------------+-----------------------------------------------+ | |
| 42 | | ``types`` | A legal function parameter list | A parenthized list of types to be displayed | | |
| 43 | | | | in the error message. | | |
| 44 | +---------------+-----------------------------------+-----------------------------------------------+ | |
| 45 | ||
| 46 | ||
| 47 | Expression semantics | |
| 48 | -------------------- | |
| 49 | ||
| 50 | For any integral constant expression ``expr``, legal C++ identifier ``message``, and | |
| 51 | arbitrary types ``t1``, ``t2``,... ``tn``: | |
| 52 | ||
| 53 | ||
| 54 | .. parsed-literal:: | |
| 55 | ||
| 56 | BOOST_MPL_ASSERT_MSG( expr, message, (t1, t2,... tn) ); | |
| 57 | ||
| 58 | :Return type: | |
| 59 | None. | |
| 60 | ||
| 61 | :Precondition: | |
| 62 | ``t1``, ``t2``,... ``tn`` are non-``void``. | |
| 63 | ||
| 64 | :Semantics: | |
| 65 | Generates a compilation error if ``expr != true``, otherwise | |
| 66 | has no effect. | |
| 67 | ||
| 68 | When possible within the compiler's diagnostic capabilities, | |
| 69 | the error message will include the ``message`` identifier and the parenthized | |
| 70 | list of ``t1``, ``t2``,... ``tn`` types, and have a general form of: | |
| 71 | ||
| 72 | .. parsed-literal:: | |
| 73 | ||
| 74 | |...| \*\*\*\*\*\*\*\*\*\*\*\*( |...|::message )\*\*\*\*\*\*\*\*\*\*\*\*)(t1, t2,... tn) |...| | |
| 75 | ||
| 76 | ||
| 77 | .. parsed-literal:: | |
| 78 | ||
| 79 | BOOST_MPL_ASSERT_MSG( expr, message, (types<t1, t2,... tn>) ); | |
| 80 | ||
| 81 | :Return type: | |
| 82 | None. | |
| 83 | ||
| 84 | :Precondition: | |
| 85 | None. | |
| 86 | ||
| 87 | :Semantics: | |
| 88 | Generates a compilation error if ``expr != true``, otherwise | |
| 89 | has no effect. | |
| 90 | ||
| 91 | When possible within the compiler's diagnostics capabilities, | |
| 92 | the error message will include the ``message`` identifier and the list of | |
| 93 | ``t1``, ``t2``,... ``tn`` types, and have a general form of: | |
| 94 | ||
| 95 | .. parsed-literal:: | |
| 96 | ||
| 97 | |...| \*\*\*\*\*\*\*\*\*\*\*\*( |...|::message )\*\*\*\*\*\*\*\*\*\*\*\*)(types<t1, t2,... tn>) |...| | |
| 98 | ||
| 99 | ||
| 100 | Example | |
| 101 | ------- | |
| 102 | ||
| 103 | :: | |
| 104 | ||
| 105 | template< typename T > struct my | |
| 106 | { | |
| 107 | // ... | |
| 108 | BOOST_MPL_ASSERT_MSG( | |
| 109 | is_integral<T>::value | |
| 110 | , NON_INTEGRAL_TYPES_ARE_NOT_ALLOWED | |
| 111 | , (T) | |
| 112 | ); | |
| 113 | }; | |
| 114 | ||
| 115 | my<void*> test; | |
| 116 | ||
| 117 | // In instantiation of `my<void*>': | |
| 118 | // instantiated from here | |
| 119 | // conversion from ` | |
| 120 | // mpl_::failed************(my<void*>:: | |
| 121 | // NON_INTEGRAL_TYPES_ARE_NOT_ALLOWED::************)(void*) | |
| 122 | // ' to non-scalar type `mpl_::assert<false>' requested | |
| 123 | ||
| 124 | ||
| 125 | See also | |
| 126 | -------- | |
| 127 | ||
| 128 | |Asserts|, |BOOST_MPL_ASSERT|, |BOOST_MPL_ASSERT_NOT|, |BOOST_MPL_ASSERT_RELATION| | |
| 129 | ||
| 130 | ||
| 131 |