108734 - nsCString::Replace is broken

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Darin Fisher]

consider this sample program:

    #include "nsString.h"

    int main(int argc, char **argv)
    {
      nsCString foo;
      foo.Assign("abc");
      printf("foo=[%s]\n", foo.get());

      foo.Replace(1, 1, nsDependentCString(argv[1]));

      printf("foo=[%s]\n", foo.get());
      return 0;
    }

when i run it i get these results:

% ./Test ""
foo=[abc]
foo=[ac]        <== good

% ./Test "f"
foo=[abc]
foo=[afc]       <== good

% ./Test "ff"
foo=[abc]
foo=[aff]       <== oops!  what happened to the 'c'

% ./Test "fff"
foo=[abc]
foo=[afff]      <== again, no 'c'

seems like a bug, since scc says:

<sccMtg> |Replace| is like a cut followed by an insert
<sccMtg> |cutLength| is the length of the range to cut

and in my example, |cutLength| is always 1.

Comment 1

[Darin Fisher]

if i substitute |Cut| + |Insert| for |Replace|, i get the correct results (ie.
the 'c' isn't lost).

this bug blocks my patch for bug 103916 (which is otherwise ready to land), so
i'll likely replace all calls to |Replace| with |Cut| + |Insert| for now.

Comment 2

[Darin Fisher]

Attachment: v1.0 patch

Comment 3

[jag (Peter Annema)]

*** Bug 108738 has been marked as a duplicate of this bug. ***

Comment 4

[jag (Peter Annema)]

|copy_string_backward| was expecting the |WritingIterator| to point to the end
of the section we wanted to write to, not the beginning, so we want to pass in
|EndWriting()| (which after the SetLength will get us exactly what we want)
instead of |BeginWriting().advance(replacementEnd)|.

Comment 5

[Darin Fisher]

Comment on attachment 56822 [details] [diff] [review]
v1.0 patch

r=darin

Comment 6

[Scott Collins]

Comment on attachment 56822 [details] [diff] [review]
v1.0 patch

sr=scc

Comment 7

[jag (Peter Annema)]

Fixed.