Checking for 'Stack size mismatch'

[Øystein Myhre Andersen]

You said:  as this error can only be detected at run time.
That is wrong. It occurs when building stack-map.

On Sat, Mar 9, 2024 at 7:38 PM - <liangchenblue at gmail.com> wrote:

> Hi Øystein,
> ClassFile API does not always ensure the created bytecode is valid, and
> allowing creation of code with invalid stack size is a feature instead of a
> bug. A stack size mismatch problem, in essence, is closer to the error
> which a user forgot to call a builder method. And putting this check
> earlier doesn't really help, as this error can only be detected at run
> time. You can always use ClassFile.verify to verify your generated class
> files.
>
> In addition, CodeBuilder supports chaining; if we add the size checking in
> each item of the chain, it will introduce a performance penalty.
>
> Chen
>
> On Sat, Mar 9, 2024 at 8:42 AM Øystein Myhre Andersen <o.myhre at gmail.com>
> wrote:
>
>> Checking for 'Stack size mismatch' is currently done in 'java.base/jdk.internal.classfile.impl.StackMapGenerator'.
>> It would have been nice if this was tested earlier by Codebuilder when the instructions was created.
>>
>> For example, by keeping track of the stack size curing code building.
>>
>> It is good programming practice to catch errors as early as possible.
>>
>>
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