Merge #21250: build: make HAVE_O_CLOEXEC available outside LevelDB (bugfix)
9bac71350d98580cc7441957fc7c3fa2f4158553 build: make HAVE_O_CLOEXEC available outside LevelDB (bugfix) (Sebastian Falbesoner)
584fd91d2d294883e6896dbd64a2176528e94581 init: only use pipe2 if availabile, check in configure (Sebastian Falbesoner)
Pull request description:
The result of the O_CLOEXEC availability check is currently only set in the Makefile and passed to LevelDB (see `LEVELDB_CPPFLAGS_INT` in `src/Makefile.leveldb.include`), but not defined to be used in our codebase. This means that code within the preprocessor conditional `#if HAVE_O_CLOEXEC` was actually never compiled. On the master branch this is currently used for pipe creation in `src/shutdown.cpp`, PR #21007 moves this part to a new module (I found the issue while testing that PR).
The fix is similar to the one in #19803, which solved the same problem for HAVE_FDATASYNC.
In the course of working on the PR it turned out that pipe2 is not available an all platforms, hence a configure check and a corresponding define HAVE_PIPE2 is introduced and used.
The PR can be tested by anyone with a system that has pipe2 and O_CLOEXEC available by putting gibberish into the HAVE_O_CLOEXEC block: on master, everything should compile fine, on PR, the compiler should abort with an error. At least that's my naive way of testing preprocessor logic, happy to hear more sophisticated ways :-)
ACKs for top commit:
Code review ACK 9bac71350d98580cc7441957fc7c3fa2f4158553