RFR: 8347831: Re-examine version check when cross linking [v8]

[Severin Gehwolf]

On Fri, 14 Nov 2025 16:00:43 GMT, Henry Jen <henryjen at openjdk.org> wrote:

>> This PR include build changes from @magicus and jlink change to verify the build signature.
>> 
>> Tested with local builds for MacOS and Linux as below shows that cross linking with same build is working while linking with different build failed with error message.
>> 
>> ❯ export JAVA_HOME=./build/macosx-x86_64-server-fastdebug/images/jdk-bundle/jdk-26.jdk/Contents/Home
>>                                                                                                                                                                  
>> ❯ java --version
>> openjdk 26-internal 2026-03-17
>> OpenJDK Runtime Environment (fastdebug build 26-internal-adhoc.hjen.JDK-8347831)
>> OpenJDK 64-Bit Server VM (fastdebug build 26-internal-adhoc.hjen.JDK-8347831, mixed mode, sharing)
>>                                                                                                                                                                  
>> ❯ jlink --version                                                                       
>> 26-internal
>>                                                                                                                                                                  
>> ❯ jlink --module-path ./build/linux-x86_64-server-release/images/jdk/jmods --add-modules java.base --output linux                                                                                                                                        
>>                                                                                                                                                                  
>> ❯ jlink --add-modules java.base --output macos
>>                                                             
>> ❯ jlink --module-path ~/linux/jdk-25.0.1/jmods --add-modules java.base --output linux25    
>> Error: jlink build N/A-26-internal-adhoc.hjen.JDK-8347831-2026-03-17 does not match target java.base build N/A
>>                                                                                                                                                                  
>> ❯ jlink --module-path /Library/Java/JavaVirtualMachines/jdk-25.jdk/Contents/Home/jmods --add-modules java.base --output macos25 
>> Error: jlink build N/A-26-internal-adhoc.hjen.JDK-8347831-2026-03-17 does not match target java.base build N/A
>
> Henry Jen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   adapt review feedbacks

src/jdk.jlink/share/classes/jdk/tools/jlink/internal/JlinkTask.java line 259:

> 257: 
> 258:             try (var r = new BufferedReader(new InputStreamReader(release.get()))) {
> 259:                 return Optional.of(r.readLine());

As suggested on the CSR we should read the entire file, not just the first line and treat the entire content as a string in a specific encoding. While I wasn't able to get the JDK build a vendor name with new lines (due to jrt-fs.jar putting `COMPANYNAME` in the MANIFEST.MF) it's conceivable that some `release.txt` file might have more than one line.

Alternatively we need to specify that the file must not contain line breaks or unusual encodings.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28155#discussion_r2541860576