45 lines
2.5 KiB
Text
45 lines
2.5 KiB
Text
unusedcode.easy is generated via callcatcher[1] and filtered to remove some
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tricky edge-cases (see Makefile), e.g. anything which could plausibly be
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dlsymed or any symbol defined in an external library bundled into LibreOffice
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which doesn't happen to get used by LibreOffice.
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unusedcode.easy is generated on an x86_64 --enable-debug --enable-dbgutil
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configuration.
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Code listed as unused is code that gcc outputs but that nothing calls
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(or takes the address of).
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a) It's possible that some other platform or configuration uses the code,
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so manual inspection is always required.
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b) At the time of writing the majority of unused code now originates via
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macros, mostly from pre-STL containers, see [2] for killing two birds
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with one stone. These are typically methods of signatures...
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*::Insert
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*::Remove
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*::DeleteAndDestroy
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*::Replace
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c) callcatcher ignores virtuals. But implementations of "pure virtuals"
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are not actually virtual methods. If something is declared pure virtual
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and provides an impl and that base-class impl is not explicitly called
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anywhere, then that impl can go away.
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d) gcc will only emit code for inlines if those inlines are used, so
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sometimes something is listed correctly as unused but some inline
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code takes a pointer or reference to something which cannot be
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instantiated so removal of some method/class fails at build time because
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gcc never emits any code for the the unused inline but trips over it at
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compile time after an attempt at removal. i.e. generally the inline method
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can go as well because nothing calls it either, a double win.
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e) if a constructor is listed as unused, and it's the *only* ctor in the class,
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then no object of that class can be constructed, so the whole thing is
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unused, which can lead to a whole cascade of tricky but logical fallout.
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f) if a destructor is listed as unused, and a constructor isn't, then there's
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a leak somewhere, and the destructor most likely *should* be called.
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g) there's more actually unused code then what's listed. The idea is that what's
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listed is definitely unused under the generation configuration, not that
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it's a list of all unused code. If the count of unused easy hits 0 then
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we can have a look at the non-easy and if that hits 0, then strip out
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code from the "release" binaries which only makes sense in debug/dbgutil
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configurations, and then tackle unused virtual method slots :-)
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[1] http://www.skynet.ie/~caolan/Packages/callcatcher.html
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[2] https://bugs.freedesktop.org/show_bug.cgi?id=38832
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