lwm2m: uninitialized variable in this function

[sinkyl]

Describe the bug
With Network, LwM2M and by default CONFIG_LWM2M_RW_JSON_SUPPORT=y in Zephyr 2.5 this warning show up:

/zephyrproject/zephyr/subsys/net/lib/lwm2m/lwm2m_rw_json.c:147:16: warning: 'c' may be used uninitialized in this function [-Wmaybe-uninitialized] 147 | uint8_t cont, c;

Environment (please complete the following information):

• OS: Linux,
• Toolchain: Zephyr SDK

[rlubos]

How to reproduce this warning? I've tried to build with zephyr-sdk-0.12.3 for x86 and arm platforms and I didn't get it.

Besides, it doesn't look like a valid warning to me. Looking at the code in https:/zephyrproject-rtos/zephyr/blob/master/subsys/net/lib/lwm2m/lwm2m_rw_json.c#L144, the c variable can only be used after being set by the buf_read_u8() call. If the function call fails, the variable won't be used, otherwise it should hold a valid value.

[sinkyl]

Try with:
CONFIG_NEWLIB_LIBC=y and
CONFIG_DEBUG=y -> just in case you don't have it...

The warning show up when newlib is set to y.

[rlubos]

Thanks, now I got it. I wonder how would these options affect the build to trigger the warning to show up...
Anyway, I still don't see anything wrong in the logic, so I'll just add some initial value to the variable to silence the warning.

[rlubos]

I've submited a fix: #32882

[sinkyl]

I don't know either...
We set the default value to 0U, what you think ??? It should be fine no ?

[rlubos]

We set the default value to 0U, what you think ??? It should be fine no ?

Yes, that's what I did as well

[sinkyl]

Thanks!