[PROTON-2241] Cannot pass integer values between 2**31 - 1 and 2**62 - 1 for pn_atom_t variables

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: proton-c-0.30.0
• Component/s: ruby-binding
• Assignee: Alan Conway
• Reporter: Ivo Wever
• Created: 20/Jun/20 10:36
• Updated: 20/Jun/20 10:42

Description

Observation

Attempting to set a number between 2**31-1 and 2**62-1 as e.g. the message-id in Ruby 2.6.5 (and probably any other recent Ruby) results in the number mod 2**32.

Example (pry is a Ruby repl):

[1] pry(main)> m = Qpid::Proton::Message.new('body')
=> Message{body="body"}
[2] pry(main)> m.id = 2**61 + 2**30
=> 2305843010287435776
[3] pry(main)> m.id
=> 1073741824

Analysis

The SWIG bindings contain the following snippet (lines 115-123)

        case T_FIXNUM:
          $1.type = PN_INT;
          $1.u.as_int = FIX2LONG($input);
          break;

        case T_BIGNUM:
          $1.type = PN_LONG;
          $1.u.as_long = NUM2LL($input);
          break;

Integer instances <= 2**62 - 1 will hit the T_FIXNUM case, as Ruby fixnums are 63 bits (1 bit is used to indicate they are fixnums to speed up arithmetic). Subsequently the number is converted into a 32 bit C long, discarding the 32 highest bits.

Further notes

The T_BIGNUM case takes care of correctly setting the value for numbers between 2**62 and 2**63-1, as those numbers can be converted into a 64 bit C long long

The T_BIGNUM case will fail for all larger numbers, with

RangeError: bignum too big to convert into `long long'

This is probably OK.

Note that the autoconversion of a pn_atom_t to an int or long is not useful for e.g. the message-id property, as it needs to be passed as a ulong (when numeric, disregarding the uuid, string, binary alternatives). Proton doesn't enforce this and naively setting message.id = 1 results in sending a message that is invalid with respect to the specification, as the type of the message-id will be an int.