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TI Home » TI E2E Community » Support Forums » Development Tools » TI C/C++ Compiler » TI C/C++ Compiler - Forum » warning #188-D: pointless comparison of unsigned integer with zero
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warning #188-D: pointless comparison of unsigned integer with zero

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Yulin
Posted by Yulin
on Mar 23 2012 05:38 AM
Intellectual930 points

Hi TI,

Is this a bug of CGTv4.9.1 ?

BR, Yulin.

---- detail ----------------------------------------------------------

typedef enum
{
 PSL_DISABLED = 0, // Don't do any power saving
 PSL_BACKLIGHT = 1, // Can turn off LCD backlight
 PSL_DISPLAY  = 2, // Can turn off screen power & LCD clocks
 PSL_SYSPOWER = 3  // Can turn off system power
}TPS;

warning #188-D enumeration
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  • George Mock
    Posted by George Mock
    on Mar 23 2012 09:12 AM
    Guru51565 points

    The argument "level" must be an unsigned type.  And, by definition, an unsigned variable is always greater than or equal to 0.  So, the compiler is trying to tell you that the test "level >= PSL_DISABLED" is always true.  Next time, add --verbose_diagnostics to your build.  That will help you see the problem.  For more discussion on diagnostics and how to handle them, see the diagnostics section of this presentation on the Wiki.

    Thanks and regards,

    -George


    TI C/C++ Compiler Forum Moderator
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  • Yulin
    Posted by Yulin
    on Mar 23 2012 10:37 AM
    Intellectual930 points

    Hi Georgem,

    Thanks for taking care of this.

    I know it is due to the test "level >= PSL_DISABLED" is always true.

    However, the function declaration "void psc_SetPowerSaveLevel(TPS level)" specifies 'level' to a TPS type instead of unsigned.

    What's wrong then ?

     

    BR,

    Yulin.

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  • George Mock
    Posted by George Mock
    on Mar 23 2012 16:22 PM
    Guru51565 points

    Yulin
    However, the function declaration "void psc_SetPowerSaveLevel(TPS level)" specifies 'level' to a TPS type instead of unsigned.

    Ah.  I overlooked that.  I suppose you could say the error message text is bit misleading.  Perhaps it should say something like the enum comparison is always true.  But that's a small thing, really.  The main point is that the comparison "level >= PSL_DISABLED" is always true.  So it is still legitimate for the compiler to issue a diagnostic.

    Thanks and regards,

    -George


    TI C/C++ Compiler Forum Moderator
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  • Norman Wong
    Posted by Norman Wong
    on Mar 23 2012 17:28 PM
    Guru14970 points

    I was under the impression that enums usually of the type "int"? The diagnostic would imply enums are "unsigned int". That would mean you could not specify a negative values in the enumeration?

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  • Yulin
    Posted by Yulin
    on Mar 23 2012 20:24 PM
    Intellectual930 points

    Both 'level' and 'PSL_DISABLED' is of type enum TPS and enum is int by default.

    Why does compiler consider 'level' unsigned ?

    I changed nothing about enum in the compiler options.

    Thanks & regards,

    Yulin.

     

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  • Archaeologist
    Posted by Archaeologist
    on Mar 26 2012 10:49 AM
    Verified Answer
    Verified by Yulin
    Mastermind40900 points

    In GCC mode, the underlying type is considered unsigned if none of the enumeration constants is negative.

    I will not guess as to why this is so.

    gcc enumeration
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