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digitalmars.D.bugs - [Issue 7992] New: std.algorithm.find breaks in certain circumstances

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=7992

           Summary: std.algorithm.find breaks in certain circumstances
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: nyphbl8d gmail.com


--- Comment #0 from William Moore <nyphbl8d gmail.com> 2012-04-26 14:57:31 PDT
---
When std.algorithm.find is used with a type that forces it to use
simpleMindedFind and the type in question supports the length attribute,
simpleMindedFind will throw an assert if the string to be searched does not
contain the search string.

For example:
struct omgstring {
        string data;
        // Start hasLength functions
         property {
                size_t length() const {return data.length;}
                void length(size_t len) {data.length = len;}
        }
        // End hasLength functions

        // Start InputRange functions
        bool empty() const {return data.empty();}
        dchar front() const {return data.front();}
        void popFront() {data.popFront();}
        // End InputRange functions

        // Start ForwardRange functions (implies InputRange)
        mycustring save() {return this;}
        // End ForwardRange functions
}

// succeeds
simpleMindedFind!"a == b"("a","b");
// throws assert when it pops past the last element
simpleMindedFind!"a == b"(to!omgstring("a"),to!omgstring("b"));

Note that I'm not actually calling simpleMindedFind directly, but that is the
function the code ends up in when throwing the assert.  The code executes
correctly if the length property is removed.

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next sibling parent d-bugmail puremagic.com writes:
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--- Comment #1 from William Moore <nyphbl8d gmail.com> 2012-04-26 15:00:48 PDT
---
Note: the structure definition is incorrect, it should be:

struct omgstring {
        string data;
        // Start hasLength functions
         property {
                size_t length() const {return data.length;}
                void length(size_t len) {data.length = len;}
        }
        // End hasLength functions

        // Start InputRange functions
        bool empty() const {return data.empty();}
        dchar front() const {return data.front();}
        void popFront() {data.popFront();}
        // End InputRange functions

        // Start ForwardRange functions (implies InputRange)
        omgstring save() {return this;}
        // End ForwardRange functions
}

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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hsteoh quickfur.ath.cx changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hsteoh quickfur.ath.cx


--- Comment #2 from hsteoh quickfur.ath.cx 2012-10-09 20:55:47 PDT ---
OK, something is very broken in simpleMindedFind(). When both haystack and
needle have the length property, estimateNeedleLength is set to false, and
estimatedNeedleLength is set to 0. Therefore, haystackTooShort() is always
false.

So in the searching loop, the if(haystackTooShort()) is skipped, and it falls
straight through to the for(auto h=haystack.save;...) loop. But here, if
h.empty is true, then because estimateNeedleLength is false, this goes straight
to "continue searching", which calls popFront() on an empty range.

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--- Comment #3 from hsteoh quickfur.ath.cx 2012-10-09 21:31:44 PDT ---
https://github.com/D-Programming-Language/phobos/pull/852

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--- Comment #4 from github-bugzilla puremagic.com 2012-10-13 14:41:24 PDT ---
Commits pushed to master at https://github.com/D-Programming-Language/phobos

https://github.com/D-Programming-Language/phobos/commit/01a690654afa50aeb1101abc734de86afbc1b552
Add unittest for issue 7992.

https://github.com/D-Programming-Language/phobos/commit/350d960f879a773296c7e553a88b0cdcf1e7a886
Merge pull request #852 from quickfur/issue7992

FIx issue 7992

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Oct 13 2012
prev sibling parent d-bugmail puremagic.com writes:
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Jonathan M Davis <jmdavisProg gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |jmdavisProg gmx.com
         Resolution|                            |FIXED


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