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<a name="Blocks"></a>
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Next: <a rel="next" accesskey="n" href="Statement-Sequences.html#Statement-Sequences">Statement Sequences</a>,
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Previous: <a rel="previous" accesskey="p" href="Basic-Statements.html#Basic-Statements">Basic Statements</a>,
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<h4 class="subsection">10.7.2 Blocks</h4>
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<p><a name="index-Blocks-1938"></a>
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Block scopes and the variables they declare in GENERIC are
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expressed using the <code>BIND_EXPR</code> code, which in previous
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versions of GCC was primarily used for the C statement-expression
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extension.
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<p>Variables in a block are collected into <code>BIND_EXPR_VARS</code> in
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declaration order through their <code>TREE_CHAIN</code> field. Any runtime
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initialization is moved out of <code>DECL_INITIAL</code> and into a
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statement in the controlled block. When gimplifying from C or C++,
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this initialization replaces the <code>DECL_STMT</code>. These variables
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will never require cleanups. The scope of these variables is just the
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body
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<p>Variable-length arrays (VLAs) complicate this process, as their
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size often refers to variables initialized earlier in the block.
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To handle this, we currently split the block at that point, and
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move the VLA into a new, inner <code>BIND_EXPR</code>. This strategy
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may change in the future.
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<p>A C++ program will usually contain more <code>BIND_EXPR</code>s than
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there are syntactic blocks in the source code, since several C++
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constructs have implicit scopes associated with them. On the
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other hand, although the C++ front end uses pseudo-scopes to
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handle cleanups for objects with destructors, these don't
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translate into the GIMPLE form; multiple declarations at the same
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level use the same <code>BIND_EXPR</code>.
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