RFR: JDK-8301497: Replace NULL with nullptr in cpu/s390

[Johan Sjölen]

On Mon, 13 Feb 2023 10:12:25 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Hi, this PR changes all occurrences of NULL to nullptr for the subdirectory cpu/s390. Unfortunately the script that does the change isn't perfect, and so we
>> need to comb through these manually to make sure nothing has gone wrong. I also review these changes but things slip past my eyes sometimes.
>> 
>> Here are some typical things to look out for:
>> 
>> 1. No changes but copyright header changed (probably because I reverted some changes but forgot the copyright).
>> 2. Macros having their NULL changed to nullptr, these are added to the script when I find them. They should be NULL.
>> 3. nullptr in comments and logs. We try to use lower case "null" in these cases as it reads better. An exception is made when code expressions are in a comment.
>> 
>> An example of this:
>> 
>> ```c++
>> // This function returns null
>> void* ret_null();
>> // This function returns true if *x == nullptr
>> bool is_nullptr(void** x);
>> 
>> 
>> Note how `nullptr` participates in a code expression here, we really are talking about the specific value `nullptr`.
>> 
>> Thanks!
>
> src/hotspot/cpu/s390/nativeInst_s390.cpp line 388:
> 
>> 386:     ShouldNotReachHere();
>> 387: #endif
>> 388:     return *(intptr_t *)nullptr;
> 
> Unnecessary cast? Also, this is de-referencing a null pointer, so we might have to do this differently after the conversion.

Code indicates that we want to crash here (sigsegv and shouldnotreachhere above).

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PR Review Comment: https://git.openjdk.org/jdk/pull/12325#discussion_r1162578083