C tests have test harness warning:

fixture.c:11:52: warning: implicitly declaring library function 'sqrt' with type 'double (double)' [-Wimplicit-function-declaration]
cr_assert_eq(IsCollision(-5, 5, 5.0001, 5, -5, 5*sqrt(5)), true, "Expected true.");
^
fixture.c:11:52: note: include the header <math.h> or explicitly provide a declaration for 'sqrt'
1 warning generated.

looks good!

Something seems off with the C random tests. For example:
< Incorrect Result >

code[13] = {
" uhefkcy mrpdrk uflndjh em zzksswz acry",
"x ogyypkkuvxpxfkajctamdsac uxqk lrsbp f",
"z zwiousp vaozd tygmv wazgstvzx rpbsdnk",
"lixlwoo mam oa ggrzui gtk k rnjcjrjy",
"xvyb gbmlhwcaerzpart dfrjhmlrvinh pvfjz",
"iqvljsba vrsv xl xw njhuq bdllcuuwxwnyw",
"ns ffmvpake q kwnezyhakbq qwxfjplh qvc",
"qfzpnf qabvstbmc bcexzj ucuolr fkov",
"dphohc dqafvqwdpdpowlbd siowt kodkcemb ",
" vepl st hkdi zt gi asvdvq rgvmjjpcuh",
"xmhapp bamj muvhnko uu ywb ynvntvnhdu ",
"eus uwg wmjkz xruttzjgmwy dyjwx ihzvdxa",
"ticc ysrrdcpmhbbzhxpjm uu oqjhikkdkhoa"
}

Submitted: "mmnikmikghmlkkiklklpkiiimjeooolknlikiok"
Expected: "i igh

iiie
i "

Why are you copying the number?

How is calling into the possibly non-trivial function pow() instead of simply writing "diff * diff" a "best practice"?

This approach has zero global ctors (which are a runtime hit).

Ugh. O(n^2) is not a "best practice IMHO.

How is making the code unreadable an improvement? Most code is meant to be read by others, and good C formatting is a virtue.

No need to use slow floating point math! :)

I feel your pain. But it kinda does -- the Description says that it uses x for rows and y for columns. It's messed up, but it is specified.

Very fine! But note you needn't pass 'cols' to floodfill (2D C arrays only need the number of columns to calculate correct the array offset).

Nice!

Note this accesses memory from high-to-low, which is non-optimal for large address ranges. So I wouldn't call this a Best Practice.

Is it me, or does this seem much harder than a 7?