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

[David Holmes]

On Fri, 18 Aug 2023 01:24:20 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> 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.

I'd missed the GrowableArray code - the other callers expect jlong/64-bit.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15233#discussion_r1297911413