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> lvm.c: In function ‘luaV_concat’:
> lvm.c:300: warning: assuming signed overflow does not occur when simplifying conditional to constant

Very wild guess:

Line293      for (n = 1; n < total && tostring(L, top-n-1); n++) {

	=> it knows that n will be strictly superior to zero (if it does not overflow), but it does not matter until...


Line300      for (i=n; i>0; i--) {  /* concat all strings */

At that line, if it knows that n>0, then it could run the first pass of the for loop without having to do the test for ending the loop. (I am not sure though that it actually would make sense optimization wise (I guess dis-assembly could comfort that guess?))

So it tells you that at line 300 it assumes that n>0 even though it might have been overflowed at line 293...

That's a wild guess really ;-)