On Tue, 19 Jul 2022 20:13:35 GMT, Dean Long <dl...@openjdk.org> wrote:

>> This patch enables lossy conversion warnings (C4244 [1]) for hotspot on 
>> Windows/MSVC. Instead of fixing all warnings that were produced from this, 
>> I've instead locally disabled the warning in the files that produced 
>> warnings. This allows gradually making progress with cleaning up these 
>> warnings on a per-file basis, instead of trying to fix all of them in one 
>> shot.
>> 
>> Out of the ~1100 files that make up hotspot on Windows x64 , ~290 have 
>> warnings for them disabled (not counting aarch64 files), which means that 
>> with this patch ~800 files are protected by enabling this warning globally.
>> 
>> Warnings can be fixed in individual files, or groups of files in followup 
>> patches, and warnings for those files can be enabled.
>> 
>> I'm working on a patch that does the same for GCC, but it produces warnings 
>> in about 150 more files, so I wanted to gather feedback on this approach 
>> before continuing with that.
>> 
>> ---
>> 
>> To disable warnings for a file, in most cases the following prelude is added 
>> after the last `#include` at the start of a file:
>> 
>>     PRAGMA_DIAG_PUSH
>>     PRAGMA_ALLOW_LOSSY_CONVERSIONS
>> 
>> And then the following is added at the end of the file for cpp files, or 
>> before closing the header guard for hpp files:
>> 
>>     PRAGMA_DIAG_POP
>> 
>> 1 notable exception are files produced by adlc, which had their code-gen 
>> modified to add these lines instead. There were also 2 files that include 
>> headers in the middle of the file (ostream.cpp & sharedRuntime.cpp), for 
>> which I've added the PRAGMA's after the include block at the start of the 
>> file instead. They only included system headers, for which disabling 
>> warnings doesn't matter any ways.
>> 
>> [1]: 
>> https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-levels-3-and-4-c4244?view=msvc-170
>
> I thought PRAGMA_DIAG_PUSH/POP are for narrowing the scope of the pragma.  So 
> unless we are concatenating .cpp files together, I would think they are not 
> needed for .cpp files if we want to affect the whole file.

@dean-long That's a good point. The PUSH and POP could be removed for the cpp 
files.

-------------

PR: https://git.openjdk.org/jdk/pull/9516

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