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74 lines
2.6 KiB
C++
74 lines
2.6 KiB
C++
// Copyright David Abrahams 2002.
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef WORKAROUND_DWA2002126_HPP
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# define WORKAROUND_DWA2002126_HPP
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// Compiler/library version workaround macro
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//
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// Usage:
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//
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// #if BOOST_WORKAROUND(BOOST_MSVC, <= 1200)
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// ... // workaround code here
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// #endif
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//
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// When BOOST_STRICT_CONFIG is defined, expands to 0. Otherwise, the
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// first argument must be undefined or expand to a numeric
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// value. The above expands to:
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//
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// (BOOST_MSVC) != 0 && (BOOST_MSVC) <= 1200
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//
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// When used for workarounds that apply to the latest known version
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// and all earlier versions of a compiler, the following convention
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// should be observed:
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//
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// #if BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1301))
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//
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// The version number in this case corresponds to the last version in
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// which the workaround was known to have been required. When
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// BOOST_DETECT_OUTDATED_WORKAROUNDS is not the defined, the macro
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// BOOST_TESTED_AT(x) expands to "!= 0", which effectively activates
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// the workaround for any version of the compiler. When
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// BOOST_DETECT_OUTDATED_WORKAROUNDS is defined, a compiler warning or
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// error will be issued if the compiler version exceeds the argument
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// to BOOST_TESTED_AT(). This can be used to locate workarounds which
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// may be obsoleted by newer versions.
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# ifndef BOOST_STRICT_CONFIG
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# define BOOST_WORKAROUND(symbol, test) \
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((symbol != 0) && (1 % (( (symbol test) ) + 1)))
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// ^ ^ ^ ^
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// The extra level of parenthesis nesting above, along with the
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// BOOST_OPEN_PAREN indirection below, is required to satisfy the
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// broken preprocessor in MWCW 8.3 and earlier.
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//
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// The basic mechanism works as follows:
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// (symbol test) + 1 => if (symbol test) then 2 else 1
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// 1 % ((symbol test) + 1) => if (symbol test) then 1 else 0
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//
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// The complication with % is for cooperation with BOOST_TESTED_AT().
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// When "test" is BOOST_TESTED_AT(x) and
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// BOOST_DETECT_OUTDATED_WORKAROUNDS is #defined,
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//
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// symbol test => if (symbol <= x) then 1 else -1
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// (symbol test) + 1 => if (symbol <= x) then 2 else 0
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// 1 % ((symbol test) + 1) => if (symbol <= x) then 1 else divide-by-zero
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//
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# ifdef BOOST_DETECT_OUTDATED_WORKAROUNDS
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# define BOOST_OPEN_PAREN (
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# define BOOST_TESTED_AT(value) > value) ?(-1): BOOST_OPEN_PAREN 1
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# else
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# define BOOST_TESTED_AT(value) != ((value)-(value))
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# endif
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# else
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# define BOOST_WORKAROUND(symbol, test) 0
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# endif
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#endif // WORKAROUND_DWA2002126_HPP
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