On Fri, 26 Feb 2021 22:15:12 GMT, Ioi Lam <ik...@openjdk.org> wrote: >> Hi, Please review >> >> Added jcmd option for dumping CDS archive during application runtime. >> Before this change, user has to dump shared archive in two steps: first run >> application with >> `java -XX:DumpLoadedClassList=<classlist> .... ` >> to collect shareable class names and saved in file `<classlist>` , then >> `java -Xshare:dump -XX:SharedClassListFile=<classlist> >> -XX:SharedArchiveFile=<archivefile> ...` >> With this change, user can use jcmd to dump CDS without going through >> above steps. Also user can choose a moment during the app runtime to dump >> an archive. >> The bug is associated with the CSR: >> https://bugs.openjdk.java.net/browse/JDK-8259798 which has been approved. >> New added jcmd option: >> `jcmd <pid or AppName> VM.cds static_dump <filename>` >> or >> `jcmd <pid or AppName> VM.cds dynamic_dump <filename>` >> To dump dynamic archive, requires start app with newly added flag >> `-XX:+RecordDynamicDumpInfo`, with this flag, some information related to >> dynamic dump like loader constraints will be recorded. Note the dumping >> process changed some object memory locations so for dumping dynamic archive, >> can only done once for a running app. For static dump, user can dump >> multiple times against same process. >> The file name is optional, if the file name is not supplied, the file >> name will take format of `java_pid<number>_static.jsa` or >> `java_pid<number>_dynamic.jsa` for static and dynamic respectively. The >> `<number>` is the application process ID. >> >> Tests: tier1,tier2,tier3,tier4 >> >> Thanks >> Yumin > > src/hotspot/share/memory/metaspaceShared.cpp line 799: > >> 797: if (strstr(file_name, ".jsa") == nullptr) { >> 798: os::snprintf(filename, sizeof(filename), "%s.jsa", file_name); >> 799: file = filename; > > This could potentially overflow the buffer. I think it's best to just leave > `file_name` alone. If the user doesn't want the `.jsa` extension, that's > fine. Similarly, we don't add `.jsa` to `-XX:ArchiveClassesAtExit` or > `-XX:SharedArchiveFile`.
How would it overflow? But I agree, I would not add jsa extension if the user did not specify one. I dislike when programs do that. ------------- PR: https://git.openjdk.java.net/jdk/pull/2737
