Why Is Comparing if an Unsigned Int >= 0 a “Pointless Comparison”?

Question

I got warning:

Pe186 \"Pointless comparison of unsigned int with zero\"

when I tried to compile the following code:

Answer 1

gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-11) in Centos 7 x86_64 does not give the warning.

But when loop index is decremented to -1, loop index is implicitly converted to a value which is equal to UINT_MAX (limits.h)

UINT_MAX + 1u is equal to 0. 0 - 1 is equal to UINX_MAX.

limits.h Various platform-dependent constants proposed by ANSI

One of alternative solution is:

unsigned int clLoop, i;

for(i = cpLoopStart+1, clLoop = i-1; i > 0; i--, clLoop = i-1)                                  
{
    //Do something
}

i will change in the range [1, cpLoopStart+1]

clLoop will change in the range [0, cpLoopStart]