RFR: 8352645: Add tool support to check order of includes

[Doug Simon]

On Sun, 23 Mar 2025 21:14:47 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

> This PR adds `bin/sort_includes.py`, a python3 script to check that blocks of include statements in C++ files are sorted alphabetically and that there's at least one blank line between user and sys includes (as per the [style guide](https://github.com/openjdk/jdk/blob/master/doc/hotspot-style.md#source-files)).
> This script can also update files with unsorted includes. The second commit in this PR shows the result of running:
> 
> python3 ./bin/sort_includes.py ./src/hotspot
> 
> To prevent an include being reordered, put at least one non-space character after the closing `"` or `>`. See `src/hotspot/share/adlc/archDesc.cpp` for an example.
> 
> Assuming this PR is integrated, jcheck could be updated to use it to ensure include statements remain sorted.

src/hotspot/cpu/aarch64/immediate_aarch64.cpp line 26:

> 24:  */
> 25: 
> 26: #include <stdlib.h>

Moving these sys includes causes a build failure: https://github.com/dougxc/jdk/actions/runs/14054959680/job/39352322113#step:12:537

In file included from /home/runner/work/jdk/jdk/src/hotspot/cpu/aarch64/immediate_aarch64.cpp:26:
/home/runner/work/jdk/jdk/src/hotspot/cpu/aarch64/immediate_aarch64.hpp:49:1: error: ‘uint64_t’ does not name a type; did you mean ‘u_int64_t’?
   49 | uint64_t logical_immediate_for_encoding(uint32_t encoding);
      | ^~~~~~~~
      | u_int64_t

The question is whether they should not be re-ordered or whether `immediate_aarch64.hpp` should add the sys includes it apparently needs.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24180#discussion_r2011659864