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add a note about variable length array

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@22278 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2005-06-24 17:22:57 +00:00
parent 543a02704e
commit e67a951720
1 changed files with 16 additions and 0 deletions
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docs/LangRef.html
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@ -717,6 +717,14 @@ be any type with a size.</p>
</td>
</tr>
</table>
<p>Note that 'variable sized arrays' can be implemented in LLVM With a zero
length array. Normally accesses past the end of an array are undefined in
LLVM (e.g. it is illegal to access the 5th element of a 3 element array).
As a special case, however, zero length arrays are recognized to be variable
length. This allows implementation of 'pascal style arrays' with the LLVM
type "{ int, [0 x float]}", for example.</p>
</div>
<!-- _______________________________________________________________________ -->
@ -1989,7 +1997,15 @@ the LLVM code for the given testcase is equivalent to:</p>
ret int* %t5
}
</pre>
<p>Note that it is undefined to access an array out of bounds: array and
pointer indexes must always be within the defined bounds of the array type.
The one exception for this rules is zero length arrays. These arrays are
defined to be accessible as variable length arrays, which requires access
beyond the zero'th element.</p>
<h5>Example:</h5>
<pre>
<i>; yields [12 x ubyte]*:aptr</i>
%aptr = getelementptr {int, [12 x ubyte]}* %sptr, long 0, uint 1