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Hello Mark,</div>
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In bytecode generation with ASM or ClassFile API, we usually do not use a fully-expanded "local variable." We use a much simpler form, a reference to a local variable slot.</div>
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Such a slot is usually allocated with `CodeBuilder::allocateLocal(TypeKind)`. If you want to create scope-local variables, first create a scope handler with `CodeBuilder::block(Consumer<BlockCodeBuilder>)`, and the slots allocated in the block will not exist
outside of the scope.</div>
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If you want to create a debug-friendly local variable (type) table entry, use the `localVariable` (used when none of your local variables have generic types) and the `localVariableType` methods. You can pass in the allocated slot and the start and end labels
of your blocks (CodeBuilder::startLabel/endLabel). This debug information is also the class-file representation of javac-generated local variables.</div>
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For stack maps: modern bytecode generation almost always come with a stack map generator; same with the ClassFile API. You don't have to worry about stack maps as the API already takes care of it for you.</div>
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Regards,</div>
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Chen Liang</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> classfile-api-dev <classfile-api-dev-retn@openjdk.org> on behalf of Mark Roberts <markro@cs.washington.edu><br>
<b>Sent:</b> Tuesday, November 12, 2024 5:45 PM<br>
<b>To:</b> classfile-api-dev@openjdk.org <classfile-api-dev@openjdk.org><br>
<b>Subject:</b> local variable creation and manipulation</font>
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<p class="x_MsoNormal">My name is Mark Roberts and I work in the University of Washington PLSE department. We have several tools the currently use BCEL to read and modify class files. I would love to replace that with the new java.lang.classfile package –
and throw away hundreds of line of code to deal with updating and maintaining StackMaps! I have only recently started to study the package so I may be missing somethings completely and please let me know if that is the case.</p>
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<p class="x_MsoNormal">My concern is that I don’t see a high level interface for creating and then using new local variables. I would like to be able to create a method scoped or a blocked scoped local variable and then be able to refer to it symbolically
in the various byte code builders.</p>
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<p class="x_MsoNormal">Thank you,</p>
<p class="x_MsoNormal">Mark</p>
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