CODECOMPOSER: CCS is warning about "pointless comparison of unsigned integer with zero" when using an enum.

Gabriel B

Intellectual 371 points

Part Number: CODECOMPOSER

Tool/software:

HI,

I want to check enum boundaries using a macro and CCS is raising the #188-D Warning.

Here's a simplification of my problem:

Because an enum can be signed or unsigned (in C23 we could fix this issue, but I think CCS only support C11) I don't see why this warning is generated.

Is this a compiler bug? Is there a way to make the compiler happy?

Regards,
Gabriel

over 1 year ago

0 Ki over 1 year ago

TI__Guru**** 474481 points

Hi Gabriel,

Is that message coming from the compiler or from the Eclipse CDT static code analysis checker? Can you provide a screenshot of the Problems view with the warning in it?

Thanks

0 Gabriel B over 1 year ago in reply to Ki

Intellectual 371 points

Hi Ki,

Thanks for your answer.

To my understanding of CCS, this is coming from the compiler.

0 Ki over 1 year ago in reply to Gabriel B

TI__Guru**** 474481 points

Thanks. I will bring this thread to the attention of the compiler experts.

0 Gabriel B over 1 year ago in reply to Ki

Intellectual 371 points

Hi Ki,

Thanks.

0 George Mock over 1 year ago in reply to Gabriel B

TI__Guru**** 251880 points

The warning diagnostic is correct. Please search the TI ARM compiler manual for the sub-chapter titled Size of Enum Types. You'll learn that the integer type underlying MyEnum_t is unsigned char. The macro IS_WITHIN forms this comparison: my_value >= MY_ENUM_A. This is a comparison of an unsigned char variable >= 0. Every unsigned char is always greater than or equal to 0, by definition. Therefore, the compiler optimizes this comparison away. It is not performed.

As for how to fix it, that depends on your intent for this code. Perhaps it makes sense to suppress the diagnostic. To learn how to do that, search the same manual for the sub-chapter titled Understanding Diagnostic Messages.

Thanks and regards,

-George

0 Keith Barkley over 1 year ago in reply to Gabriel B

Guru 42425 points

If you are just using the enums as enums and not using the integer value for anything, just start it at 1.

0 Gabriel B over 1 year ago

Intellectual 371 points

Thanks George Mock and Keith Barkley for your answers.

I understand that this is not an unwanted behavior; even if I don't find it intuitive.
I will therefore close this issue.

For people finding this thread; my prefered solution is to break the >= into > || ==.

By doing this, the compiler doesn't realize that the combination is always true when MIN is 0.

#define IS_WITHIN(number_, min_, max_)                 (((number_) > (min_) || (number_) == (min_)) && (number_) <= (max_))

Best regards,

Gabriel

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CODECOMPOSER: CCS is warning about "pointless comparison of unsigned integer with zero" when using an enum.