Fix type formating for lifetime

[tgagneret-embedded]

I'm using Anjay on a MCU and I'm facing an issue with the conversion of lifetime using vnsprintf because %lld is not supported.

Since the specification gives lifetime as a 32bit integer we can use %li instead to make it work.

You can find the definition of lifetime p76: LWM2M Spécification

You can find the C data type here : C Data types

[kFYatek]

Hi, first of all thank you for using Anjay and for your contribution! This is much appreciated!

However, I'm sorry, but I don't think we can accept your patch like this. Here is my reasoning for sticking to 64-bit integers there:

• Page 76 of the TS you link to, the "32-bit integer" only refers to the fact that 32-bit encoding is used for that value in the TLV format. As you can read in Appendix C (page 92), a value of type Integer "may be 1 (8-bit), 2 (16-bit), 4 (32-bit) or 8 (64-bit) bytes long". We comply with this by always sending the most compact representation possible over the network when using the TLV format.
• In the same Appendix C (page 92), you can read that in LwM2M, the Integer type is defined as "An 8, 16, 32 or 64-bit signed integer. The valid range of the value for a Resource SHOULD be defined." The range for the Lifetime Resource is not defined (see the definition of the LwM2M Server object in Appendix E.2, page 101). Due to this fact, we assume the largest range possible, which is 64-bit in this case.
• 64-bit integers are used in Anjay extensively for internally handling and passing values of all Resources of the Integer data type.
• Your patch only addresses the lt parameter in the Register/Update messages, even though there are number of other places where %lld and similar formats are used - most notably in the implementations of the plain-text and JSON data formats. Your patch would result in an unfortunate inconsistency - it may fix the problem with Register message for you, but you are likely to run into more problems when the server starts actually manipulating resources anyway.

I suppose that the C library implementation that you use on your MCU may have a "larger" variant that includes support for 64-bit integers in printf()/scanf() family of functions. This is currently required for Anjay to work properly.

However, we acknowledge the problem that requiring full 64-bit integer support, including formatted I/O, is a problem for many small embedded platform. We will look into possibilities of resolving this issue in future versions.