RFR: 8314265: Fix -Wconversion warnings in miscellaneous runtime code [v6]

[Coleen Phillimore]

On Fri, 18 Aug 2023 00:24:07 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> If they stay jlong returns (note that these fields are in fact int), then we need to add casting to all the callers.  Casting is worse than returning the correct types.  If someone wants to make these fields jlong someday then they can propagate the change to the callers.  This change corrects the types.
>
> I don't follow. The fields are int so cast them to jlong before returning them. All the callers of these methods expect jlong so there can't be any issue there.

You don't need to cast from int to jlong.   The callers of these methods expect int:


src/hotspot/share/services/threadService.cpp:1103:55: warning: conversion from 'jlong' {aka 'long int'} to 'int' may change value [-Wconversion]
 1103 |   int init_size = ThreadService::get_live_thread_count();
      |                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~


Changing int to jlong here, gets a new warning:


src/hotspot/share/services/threadService.cpp:1104:54: warning: conversion from 'jlong' {aka 'long int'} to 'int' may change value [-Wconversion]
 1104 |   _threads_array = new GrowableArray<instanceHandle>(init_size);
      |                                                      ^~~~~~~~~


If you look up in the header file, the field is an int.  It makes sense to return an int:


  static volatile int  _atomic_threads_count;
  static volatile int  _atomic_daemon_threads_count;


Correcting the types means returning a type that matches the declaration so that its consistent.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15233#discussion_r1297894123