| [2] | 1 | The collector uses a large amount of conditional compilation in order to
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| 2 | deal with platform dependencies. This violates a number of known coding
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| 3 | standards. On the other hand, it seems to be the only practical way to
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| 4 | support this many platforms without excessive code duplication.
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| 5 |
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| 6 | A few guidelines have mostly been followed in order to keep this manageable:
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| 7 |
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| 8 | 1) #if and #ifdef directives are properly indented whenever easily possible.
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| 9 | All known C compilers allow whitespace between the "#" and the "if" to make
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| 10 | this possible. ANSI C also allows white space before the "#", though we
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| 11 | avoid that. It has the known disadvantages that it differs from the normal
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| 12 | GNU conventions, and that it makes patches larger than otherwise necessary.
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| 13 | In my opinion, it's still well worth it, for the same reason that we indent
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| 14 | ordinary "if" statements.
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| 15 |
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| 16 | 2) Whenever possible, tests are performed on the macros defined in gcconfig.h
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| 17 | instead of directly testing patform-specific predefined macros. This makes it
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| 18 | relatively easy to adapt to new compilers with a different set of predefined
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| 19 | macros. Currently these macros generally identify platforms instead of
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| 20 | features. In many cases, this is a mistake.
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| 21 |
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| 22 | 3) The code currently avoids #elif, eventhough that would make it more
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| 23 | readable. This was done since #elif would need to be understood by ALL
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| 24 | compilers used to build the collector, and that hasn't always been the case.
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| 25 | It makes sense to reconsider this decision at some point, since #elif has been
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| 26 | standardized at least since 1989.
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| 27 |
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| 28 | Many of the tested configuration macros are at least somewhat defined in
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| 29 | either include/private/gcconfig.h or in Makefile.direct. Here is an attempt
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| 30 | at defining some of the remainder: (Thanks to Walter Bright for suggesting
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| 31 | this. This is a work in progress)
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| 32 |
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| 33 | MACRO EXPLANATION
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| 34 | ----- -----------
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| 35 |
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| 36 | __DMC__ Always #define'd by the Digital Mars compiler. Expands
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| 37 | to the compiler version number in hex, i.e. 0x810 is
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| 38 | version 8.1b0
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| 39 |
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| 40 | _ENABLE_ARRAYNEW
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