RFR: 8303942: FileMapInfo::write_bytes aborts on a short os::write

[Afshin Zafari]

On Mon, 3 Apr 2023 00:46:36 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> We have other cases that assumes that `os::write` writes all the requested bytes:
> 
> https://github.com/openjdk/jdk/blob/aa762102e9328ca76663b56b3be6f6141b044744/src/hotspot/share/jfr/recorder/repository/jfrEmergencyDump.cpp#L379-L389
> 
> Writing a loop for each case will be messy and buggy. It's better to get rid of `os::write()` and replace it with `os::write_fully()`.
> 
> ```
> size_t bytes_written = os::write_fully(fd, buffer, bytes_requested);
> if (bytes_written != bytes_requested) {
>     // report error ....
> }
> ```
> 
> and I can't understand why `os::write` takes an `unsigned int`!
> 
> https://github.com/openjdk/jdk/blob/aa762102e9328ca76663b56b3be6f6141b044744/src/hotspot/os/posix/os_posix.cpp#L774-L778

For the `signed` and `unsigned` question, please refer to my reply to David's comment above. 

All cases that found are:

#### using `write()` in loop:
  src/hotspot/os/posix/perfMemory_posix.cpp
  src/hotspot/share/jfr/writers/jfrStreamWriterHost.inline.hpp
  src/hotspot/share/services/heapDumperCompression.cpp

#### buggy use of `write()`:
  src/hotspot/share/jfr/recorder/repository/jfrEmergencyDump.cpp
  src/hotspot/share/prims/jvm.cpp (Issue 8303943 is already created for it)
  src/hotspot/share/cds/filemap.cpp (The current issue is for it)

So, shall we create a new issue for the remaining buggy case and then create another issue for replacing all the loop cases with a new `write_fully()`? Or do all these in one new issue?

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PR Comment: https://git.openjdk.org/jdk/pull/13188#issuecomment-1493939178