Compiling lv_log.c fails due to type limits error

[Ferruck]

Hi!

When compiling LittlevGL with the GCC 7.3.1 provided by Arm (arm-bare-none-eabi) with -Wall, -Wextra and -Werror activated and LV_LOG_LEVEL set to LV_LOG_LEVEL_TRACE, compilation fails with the following error

lv_log.c:61:14: error: comparison is always true due to limited range of data type [-Werror=type-limits]
     if(level >= LV_LOG_LEVEL) {
              ^~
cc1: all warnings being treated as errors

because level is a lv_log_level_t (which is a typedef for uint8_t) and LV_LOG_LEVEL_TRACE equals 0.

There are multiple possibilities how to fix this (in case you think that this is an error, too):

• Start enumerating log levels with 1
• Use a non-unsigned integer type for lv_log_level_t
• Enumerate log levels in a way that bitwise comparisons could be done
• Streamline the definitions of the log macros in a way that the comparison is completely superfluous (though this would imply that lv_log_add() is kinda internal and shall be used exclusively through the log macros)
• Add compiler pragmas for "downgrading" this to a warning
• Your obvious solution that I didn't think of

I'd gladly provide a patch for any of the above if you like and – again – if you think this is an issue, too, otherwise feel free to simply close this issue.

Regards

[embeddedt]

@Ferruck Considering that we aren't likely to have 128 log levels anytime soon, I think using a signed integer type might be the cleanest method.

[kisvegabor]

@Ferruck Thank you for the clear report and suggestion!

I merged your patch!

[Ferruck]

No problem, you're welcome.