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112 lines
2.2 KiB
112 lines
2.2 KiB
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Notes on how to deal with the wicked corner case that is C/C++
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preprocessor #if magic. None of this is actually implemented.
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Languages not affected:
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- D
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- Java
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- ECMA (Java Script)
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Langauges affected:
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- C
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- C++
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- C#
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- Vala
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- Pawn
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- Objective C/C++
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Threads of code are created for functions that navigate the tokens.
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There is the master list of the raw tokens parsed out.
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There is at least one thread, which, in the absense of any #if statements, is
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the same as the raw token list.
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In the threads, a BARRIER is placed where ever code cannot move past.
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This represents and #if or #else statement.
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Normally, the barriers are skipped when navigating code. Only when removing a
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newline does the code need to check for a barrier.
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For #if statements without an #else, there is an implicit #else added that contains
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nothing.
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// example 1
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a
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#if X
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b
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#endif
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c
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Thread
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#if #endif
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V V
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0 - a -+- b -+- c
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1 +-----+ <- empty else path (ie, for '#if 0')
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Max depth = 2
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// example 2
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a
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#if X
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b
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#else
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c
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#endif
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d
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#if #endif
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V V
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0 - a -+- b -+- d
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1 +- c -+ <- else path
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Max depth = 2
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// example 3
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a
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#if X
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b
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#elif Y
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c
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#elif Z
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d
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#else
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e
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#endif
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f
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#if A
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g
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#endif
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h
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#if X #endif #if A
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V V V
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0 - a -+- b -+- f -----------+- g -+- h
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1 +- c -+ <- elif Y +-----+ <- empty else
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2 +- d -+ <- elif Z
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3 +- e -+ <- else
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Max depth = 4
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The detection routines need to be executed once for each thread, up to the maximum
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thread depth. Note that the typical maximum thread depth is going to be 2-3.
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0 - a - b - f - g - h
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1 - a - c - f ----- h
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2 - a - d - f - g - h
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3 - a - e - f - g - h
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The general rule is that if the current thread exceed the max, thread 0 is used.
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Identification is the primary use for the threads.
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The secondary use is indentation. The indentation of each token at each thread
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level is recorded.
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The maximum indentation for the token is used, assuming the thread is without
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error. ('#if 0' commented out code that is bad may not be handled.)
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I won't know if this will work for sure until I try it.
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