RFR: 8286562: GCC 12 reports some compiler warnings [v8]

[Yasumasa Suenaga]

On Wed, 25 May 2022 01:50:57 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Yasumasa Suenaga has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 11 commits:
>> 
>>  - Merge remote-tracking branch 'upstream/master' into gcc12-warnings
>>  - Use getter function to access "_data"
>>  - Revert changes for bytecodeAssembler.cpp, classFileParser.cpp, symbolTable.cpp
>>  - revert changes for memnode.cpp and type.cpp
>>  - Add assert to check the range of BasicType
>>  - Merge remote-tracking branch 'upstream/master' into HEAD
>>  - Revert change for java.c , parse_manifest.c , LinuxPackage.c
>>  - Calculate char offset before realloc()
>>  - Use return value from JLI_Snprintf
>>  - Avoid pragma error in before GCC 12
>>  - ... and 1 more: https://git.openjdk.java.net/jdk/compare/c156bcc5...042c1c70
>
> src/hotspot/share/oops/array.hpp line 102:
> 
>> 100:   // standard operations
>> 101:   int  length() const                 { return _length; }
>> 102:   T* data() const                     { return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(this) + base_offset_in_bytes()); }
> 
> Adding the const-qualifier to the `data()` function and then implicitly
> casting it away (by casting through intptr_t) is wrong.  Either don't
> const-qualify (and leave it to some future use that needs such to address
> appropriately), or have two functions.  Also, the line length is excessive.
> So this:
> 
> 
> T* data() {
>   return reinterpret_cast<T*>(
>     reinterpret_cast<char*>(this) + base_offset_in_bytes());
> }
> 
> and optionally add this:
> 
> const T* data() const {
>   return reinterpret_cast<const T*>(
>     reinterpret_cast<const char*>(this) + base_offset_in_bytes());
> }

Thanks a lot @kimbarrett !

I updated around stringop-overflow warning in jfrTraceIdBits.inline.hpp , and added two `data()` in `Array` class. They works fine on my GCC 12 on Fedora 36. Could you review again?

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PR: https://git.openjdk.java.net/jdk/pull/8646