ERL-49: Large halt() exit status not checked

[OTP-Maintainer]

Original reporter: richardc
Affected version: OTP-18.2
Fixed in version: OTP-18.3
Component: erts
Migrated from: https://bugs.erlang.org/browse/ERL-49

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In halt/1 and halt/2, if the given Status is a fixnum, it gets negated and cast to an int in the function halt_1 (bif.c), which typically truncates it to 32 bits. If the original value was large enough (e.g. 7FFFFFFE), the negated and truncated value can overlap with the definitions of ERTS_ABORT_EXIT and friends (sys.h), which are in the range INT_MIN...(INT_MIN+2), causing the system to exit with a crash dump and/or core dump.

Example:
{code:erlang}
1> halt(16#7FFFFFFE).
Crash dump is being written to: /tmp/erl_crash_dump...done

1> halt(16#7FFFFFFF).
Aborted (core dumped)

1> halt(16#80000001).
Crash dump is being written to: /tmp/erl_crash_dump...done
Aborted (core dumped)
{code}

Possible solutions that I've looked at:
* Set a hard upper limit for the halt() status codes, same on all Erlang systems; e.g., 7FFFFFF0. Consistent, but not so nice on systems that want to use a full 32-bit range for error codes.
* Check for an upper limit of e.g. INT_MAX-7, which could potentially vary between systems. Inconsistent from the Erlang programmer's view, awkward to document, and still doesn't allow full 32 bit range on normal systems.
* Silently truncate the value to at most N bits where N is as large as possible but not large enough to cause the value to wrap. Inconsistent, hackish, and doesn't allow full 32 bits.
* Rewrite the mechanism for setting these internal exit flags (ERTS_INTR_EXIT, ERTS_ABORT_EXIT, ERTS_DUMP_EXIT) to separate them from the exit code, so at least 32 bits can be guaranteed if the OS allows it. Consistent and much nicer, but I don't want to attack that part of the code without some feedback from the OTP devs first.

[OTP-Maintainer]

richardc said:

Related to https://github.com/erlang/otp/pull/911.

[OTP-Maintainer]

bruce said:

Just a tip for pull requests, if you mention "ERL-49" in the description or title of the Github pull request, it will be shown here automatically on JIRA. 

Example: http://bugs.erlang.org/browse/ERL-43

[OTP-Maintainer]

sverker said:

Any non negative exit status is now accepted by halt. High order bits will be truncated if not supported by the OS.