RFR: JDK-8301479: Replace NULL with nullptr in os/linux

[Johan Sjölen]

On Tue, 31 Jan 2023 10:15:48 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

> Hi, this PR changes all occurrences of NULL to nullptr for the subdirectory os/linux. Unfortunately the script that does the change isn't perfect, and so we
> need to comb through these manually to make sure nothing has gone wrong. I also review these changes but things slip past my eyes sometimes.
> 
> Here are some typical things to look out for:
> 
> 1. No changes but copyright header changed (probably because I reverted some changes but forgot the copyright).
> 2. Macros having their NULL changed to nullptr, these are added to the script when I find them. They should be NULL.
> 3. nullptr in comments and logs. We try to use lower case "null" in these cases as it reads better. An exception is made when code expressions are in a comment.
> 
> An example of this:
> 
> ```c++
> // This function returns null
> void* ret_null();
> // This function returns true if *x == nullptr
> bool is_nullptr(void** x);
> 
> 
> Note how `nullptr` participates in a code expression here, we really are talking about the specific value `nullptr`.
> 
> Thanks!

Found some things to fix

src/hotspot/os/linux/cgroupSubsystem_linux.hpp line 169:

> 167:   err = subsystem_file_line_contents(subsystem,                           \
> 168:                                      filename,                            \
> 169:                                      nullptr,                                \

Align

src/hotspot/os/linux/cgroupSubsystem_linux.hpp line 187:

> 185:   err = subsystem_file_line_contents(subsystem,                           \
> 186:                                      filename,                            \
> 187:                                      nullptr,                                \

Align

src/hotspot/os/linux/cgroupSubsystem_linux.hpp line 191:

> 189:                                      variable);                           \
> 190:   if (err != 0)                                                           \
> 191:     return (return_type) nullptr;                                            \

Align

src/hotspot/os/linux/os_linux.cpp line 2177:

> 2175: 
> 2176:   p = OSContainer::cpu_cpuset_memory_nodes();
> 2177:   st->print_cr("cpu_memory_nodes: %s", p != null ? p : "not supported");

Glitched out

src/hotspot/os/linux/os_linux.cpp line 3312:

> 3310: 
> 3311: // Allocate (using mmap, NO_RESERVE, with small pages) at either a given request address
> 3312: //   (req_addr != null) or with a given alignment.

nullptr

src/hotspot/os/linux/os_linux.cpp line 3840:

> 3838: 
> 3839:   // Since shmid has been setup with SHM_HUGETLB, shmat will automatically
> 3840:   // return large page size aligned memory addresses when req_addr == null.

nullptr

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

PR: https://git.openjdk.org/jdk/pull/12315