On Sat, 20 Jul 2024 08:02:34 GMT, Thomas Stuefe <stu...@openjdk.org> wrote:
>> src/hotspot/share/services/diagnosticArgument.hpp line 66: >> >>> 64: public: >>> 65: char *_name; >>> 66: }; >> >> Something is off about this. What is the lifetime of this object? >> >> You don't free it. Running a command in a loop will consume C-heap (you can >> check this with NMT: `jcmd VM.native_memory baseline`, then run a command >> 100 times, then `jcmd VM.native_memory summary.diff` will show you the leak >> in mtInternal. >> >> I would probably just inline the string. E.g. >> >> >> struct FileArgument { >> char name[max name len] >> }; >> >> >> FileArguments sits as member inside DCmdArgument. DCmdArgument or >> DCmdArgumentWithParser sits as member in the various XXXDCmd classes. >> >> Those are created in DCmdFactory::create_local_DCmd(). Which is what, a >> static global list? So we only have one global XXXDCmd object instance per >> command, but for each command invocation re-parse the argument values? What >> a weird concept. >> >> Man, this coding is way too convoluted for a little parser engine :( >> >> But anyway, inlining the filename array into FileArgument should be probably >> fine from a size standpoint. I would, however, not use JVM_MAXPATHLEN or >> anything that depends ultimately on PATH_MAX from system headers. We don't >> want the object to consume e.g. an MB if some crazy platform defines >> PATH_MAX as 1MB. Therefore I would use e.g. 1024 as limit for the path name. >> >> (Note that PATH_MAX is an illusion anyway, there is never a guarantee that a >> path is smaller than that limit... See this good article: >> https://insanecoding.blogspot.com/2007/11/pathmax-simply-isnt.html) > > Note that the reason for the leak is probably the fact that you don't clear > old values on parse_value. See e.g. how char* does it. However, since you > allocate with a constant size anyway, the buffer size never changes, you > could just as well either follow my advice above (inlining), or just re-use > the existing pointer. Hi Thomas, Yes - this was an oversight on my end. I was not directly calling the `destroy_value()` function. I tried to follow more closely what’s done for `char*`, as I like the consistency throughout. I did a quick check and I don’t see any more leaks with NMT. Does the new change make sense to you as well? Thank you for the feedback! ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20198#discussion_r1687081245