RFR: 8034066: Incorrect alignment in the "Code" section for "-c -XDdetails" options

[Chen Liang]

On Thu, 24 Oct 2024 14:57:19 GMT, Jonathan Lampérth <duke at openjdk.org> wrote:

> This PR includes changes to ensure `Code:` block indentation in `javap`for the `-verbose` case and non `-verbose` case is the same, which currently does not hold.
> 
> Current behaviour of `javap` differs with and without `-verbose` in the following way:
> **Command**: `javap -c -XDdetails:stackMaps A.class`
> 
> Without `-verbose`
> 
> 
> ...
>   public void a();
>     Code:
>        0: iconst_0
>        1: istore_1
>     StackMap locals:  this int
>     StackMap stack:
> ...
> 
> 
> With `-verbose`
> 
> 
> ...
>   public void a();
>     descriptor: ()V
>     flags: (0x0001) ACC_PUBLIC
>     Code:
>       stack=2, locals=2, args_size=1
>          0: iconst_0
>          1: istore_1
>       StackMap locals:  this int
>       StackMap stack:
> ...
> 
> 
> With `-verbose` all contents of the `Code:` section include an extra (2 space) indent, which is missing in the non `-verbose` case. This is because the `CodeWriter` is called via `CoderWriter.write(...)` in the `-verbose` case, which wraps the `Code:` block in `indent(+1);...indent(-1)`.
> 
> In the non-verbose case this call is circumvented and a simplified version of `CoderWriter.write(...)` is included directly in `ClassWriter.writeMethod`.
> 
> ---
> 
> Alternatively to keep the logic within `CodeWriter` with the goal of keeping the logic for `-verbose` and non `-verbose` in the same place one could add `CodeWriter.writeSimple(...)`.
> 
> 
> void writeSimple(CodeAttribute attr) {
>         println("Code:");
>         indent(+1);
>         writeInstrs(attr);
>         writeExceptionTable(attr);
>         indent(-1);
>     }
> 
> 
> ---
> 
> Note: Test setup is inspired by existing tests: [T6622232.java](https://github.com/openjdk/jdk/blob/master/test/langtools/tools/javap/T6622232.java) and [8244573](https://github.com/openjdk/jdk/blob/master/test/langtools/tools/javap/8244573)

test/langtools/tools/javap/8034066/EmptyLoop.jcod line 26:

> 24:  /*
> 25:  * Original source:
> 26:  * public class EmptyLoop {

To reduce test file noise, I recommend adding this as a package-private class to the end of your test file (so not a nested class) after it is renamed, like:


class EmptyLoop {
    public void emptyLoop() {
        for (int i = 0; i < 10; i++) {
        }
    }
}


After that, once your test class is compiled, the `EmptyLoop.class` is available in `test.classes` property directory, so you can remove this jcod and all code that converts the jcod to class.

You can see UndefinedAccessFlagTest for how we use such tricks.

Note: since you will only have one test class, you no longer need a dedicated directory; you can just place our `CodeIndentTest.java` in the root javap directory.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/21685#discussion_r1815931722