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Re^3: How is perl able to handle the null byte?

by fizbin (Chaplain)
on Jun 16, 2006 at 18:58 UTC ( #555853=note: print w/ replies, xml ) Need Help??


in reply to Re^2: How is perl able to handle the null byte?
in thread How is perl able to handle the null byte?

Well, especially for builtins perl should know if the char* it's handing off to the system call will be interpreted as a classic C string or as a wide character.

I question strongly that this is a serious performance issue - among other things, null-containing strings could easily be flagged as such, the way tainted strings are when running under taint mode.

As for what perl should do, I certainly think that a warning when running under -w is appropriate - this is at least as big a problem as interpolating an undef variable into a string. I might even be convinced that perl in taint mode should treat nul-containing strings as tainted when passing them to C APIs - that is, die.

--
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Re^4: How is perl able to handle the null byte?
by BrowserUk (Pope) on Jun 16, 2006 at 19:57 UTC
    I question strongly that this is a serious performance issue ...

    Think again.

    The taint flag is set at a few, very specific points of input. And it remains set until it is modified

    Think of all the different ways a string can be read in, constructed or modified. Interpolation of other strings, concatenation, join, pack, unpack, qq//, s///, tr///, substr, chomp, chop, sprintf, read, sysread, vec, promotion of IVs & NVs to PVs etc. etc. Every time a scalar is modified it would be necessary to recheck whether it now (or still) contains one or more null characters--and if it does, whether they are a legitimate part of a multibyte character or not.

    Still doubt the performance impact?


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