Zephyr SDK's newlib doesn't support long long specifiers in printf

[pfalcon]

In a Zephyr application with CONFIG_NEWLIB_LIBC, I'm doing printf("%lld\n", foo); and get ld as output. Ditto for "%llu".

According to https://stackoverflow.com/a/32949522/496009, newlib's long long printf support is disabled by default, and must be enabled with --enable-newlib-io-long-long option to configure.

We should consider whether we want to enable that. But not having support for 64-bit value printing is weird.

(Report is based on samples/net/sockets/sntp_client's usage of LOG_DBG("time: %lld", epoch_time);. That doesn't work (what's printed is time: ERR). Heck, even printf("%lld") doesn't work.)

[pfalcon]

@galak, @nashif: Any comments?

[galak]

Let's create a build of the SDK with long long enabled and see the size comparison

[galak]

Let's create a build of the SDK with long long enabled and see the size comparison

Since we set --enable-newlib-nano-formatted-io today, we need to disable that as the nano-formatted-io doesnt support long long.

[pfalcon]

Let's create a build of the SDK with long long enabled and see the size comparison

Do you mean comparison for generated code size? Sounds good, thanks.

[pfalcon]

@galak: This is now going to be a blocker for GoogleIoT, due to GoogleCloudPlatform/iot-device-sdk-embedded-c@d215cc5#diff-6e458435d7562e1520557ee84e6791bc . Let's please do something about this. (If I should do something about this, please let me know. I didn't look into Zephyr SDK build process, so it may take a while for me to achieve something.)

[pfalcon]

This is now going to be a blocker for GoogleIoT

Ticketed as atigyi/zephyr#5

[galak]

is there an existing sample or test that uses long long?

[galak]

#101

Need to see how this impacts code size.

[pfalcon]

is there an existing sample or test that uses long long?

Do you mean in Zephyr tree?

Grepping, following tests/samples use it: samples/net/gptp, tests/net/ipv6. It's unclear how easy would be use them to test the functionality though.

And overall, there's a bit of hacking around it already in the codebase, e.g. (docstring for printk()):

 * Length attributes h, hh, l, ll and z are supported. However, integral
 * values with %lld and %lli are only printed if they fit in a long
 * otherwise 'ERR' is printed. Full 64-bit values may be printed with %llx.

We definitely can/should add a dedicated test for libc + %lld/%llu.

[pfalcon]

#101

Thanks! I'm off tomorrow, by otherwise, let me bootstrap SDK building env and try it.

[galak]

Thanks! I'm off tomorrow, by otherwise, let me bootstrap SDK building env and try it.

If you wait for CI to pass, I'll post the link to where you can get a binary.

[pfalcon]

If you wait for CI to pass, I'll post the link to where you can get a binary.

Definitely will help, thanks!

[galak]

Definitely will help, thanks!

builds.zephyrproject.org/zephyrproject-rtos/sdk-ng/101/zephyr-sdk-0.10.3-pr-101-setup.run