Unfortunately there's no way to elegantly do this with pre-canned
algorithms. Using a generating iterator doesn't work because you default
construct for each element, then move construct into the actual slot
(bad for copy but non-movable types, and a little unneeded overhead even
in the move-only case), so just write it out manually.
This solution isn't exception safe (if one of the element's ctors calls
we don't fall back, destroy the constructed elements, and throw on -
which std::uninitialized_fill does do) but SmallVector (and LLVM) isn't
exception safe anyway.
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(& because it makes it easier to test, this also improves
correctness/performance slightly by moving the last element in an insert
operation, rather than copying it)
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This would cause the last element in a range to be in a moved-from state
after an insert at a non-end position, losing that value entirely in the
process.
Side note: move_backward is subtle. It copies [A, B) to C-1 and down.
(the fact that it decrements both the second and third iterators before
the first movement is the subtle part... kind of surprising, anyway)
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When we were moving from a larger vector to a smaller one but didn't
need to re-allocate, we would move-assign over uninitialized memory in
the target, then move-construct that same data again.
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r206916 was not logically the same as the previous code because the
goto statements did not create loop. This should be the same as the
previous code.
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Goto statements jumping into previous inner blocks are pretty confusing
to read even though in this case they are valid. No reason to not use
while loops there.
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This reverts commit r203374.
Ambiguities in assign... oh well. I'm just going to revert this and
probably not try to recommit it as it's not terribly important.
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Move a common utility (assign(iter, iter)) into SmallVector (some of the
others could be moved there too, but this one seemed particularly
generic) and replace repetitions overrides with using directives.
And simplify SmallVector::assign(num, element) while I'm here rather
than thrashing these files (that cause everyone to rebuild) again.
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This reverts commit 617330909f.
It broke the bots:
/home/clangbuild2/clang-ppc64-2/llvm.src/unittests/ADT/SmallVectorTest.cpp:150: PushPopTest
/home/clangbuild2/clang-ppc64-2/llvm.src/unittests/ADT/SmallVectorTest.cpp:118: Failure
Value of: v[i].getValue()
Actual: 0
Expected: value
Which is: 2
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if the vector is not empty. This will ensure that calls to these functions
will reference elements in the vector.
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Rationale:
1) This was the name in the comment block. ;]
2) It matches Clang's __has_feature naming convention.
3) It matches other compiler-feature-test conventions.
Sorry for the noise. =]
I've also switch the comment block to use a \brief tag and not duplicate
the name.
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* wrap code blocks in \code ... \endcode;
* refer to parameter names in paragraphs correctly (\arg is not what most
people want -- it starts a new paragraph).
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test more than a single instantiation of SmallVector.
Add testing for 0, 1, 2, and 4 element sized "small" buffers. These
appear to be essentially untested in the unit tests until now.
Fix several tests to be robust in the face of a '0' small buffer. As
a consequence of this size buffer, the growth patterns are actually
observable in the test -- yes this means that many tests never caused
a grow to occur before. For some tests I've merely added a reserve call
to normalize behavior. For others, the growth is actually interesting,
and so I captured the fact that growth would occur and adjusted the
assertions to not assume how rapidly growth occured.
Also update the specialization for a '0' small buffer length to have all
the same interface points as the normal small vector.
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The rationale here is that it's hard to write loops containing vector erases and
it only shows up if the vector contains non-trivial objects leading to crashes
when forming them out of garbage memory.
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It always returns the iterator for the first inserted element, or the passed in
iterator if the inserted range was empty. Flesh out the unit test more and fix
all the cases it uncovered so far.
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Note that support for rvalue references does not imply support
for the full set of move-related STL operations.
I've preserved support for an odd little thing in insert() where
we're trying to support inserting a new element from an existing
one. If we actually want to support that, there's a lot more we
need to do: insert can call either grow or push_back, neither of
which is safe against this particular use pattern.
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vec.insert(vec.begin(), vec[3]);
The issue was that vec[3] returns a reference into the vector, which is invalidated when insert() memmove's the elements down to make space. The method needs to specifically detect and handle this case to correctly match std::vector's semantics.
Thanks to Howard Hinnant for clarifying the correct behavior, and explaining how std::vector solves this problem.
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is partly because this attribute caused trouble in the past (the
SmallVector one had to be changed from aligned to aligned(8) due
to causing crashes on i386 for example; in theory the same might
be needed in the Allocator case...). But it's mostly because
there seems to be no point in special casing gcc here. Using the
same implementation for all compilers results in better testing.
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capacity and remove the workaround in SmallVector<T,0>. There are some
theoretical benefits to a N->2N+1 growth policy anyway.
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I think there are good reasons to change this, but in the interests
of short-term stability, make SmallVector<...,0> reserve non-zero
capacity in its constructors. This means that SmallVector<...,0>
uses more memory than SmallVector<...,1> and should really only be
used (unless/until this workaround is removed) by clients that
care about using SmallVector with an incomplete type.
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