A precompile panic aborts the block rather than the call, so both of these
stopped every validator on any chain with stableswap enabled.
An amplification coefficient of zero divides by zero in all three Newton ops --
computeY's c/(A*n*n) and D/(A*n), and computeD's denominator (A*n-1)*D +
(n+1)*dP, which crosses exactly zero. A 40,000-input sweep hit it 665 times. A
is now read and refused at the boundary, which is also the honest answer: the
invariant is undefined at A=0.
addLiquidity divides by D0, and computeD returns zero for an empty pool.
Balances and totalSupply arrive as independent calldata, so "no assets, LP
tokens outstanding" is reachable. Post-fix sweep: zero panics in 40,000 inputs.
computeY used floor division, so its iterates drifted BELOW the true root in
55% of solves, by up to 2 wei, which getDy's single -1 margin did not cover.
The invariant therefore DECREASED across a swap -- 27 losses in 19,996 random
swaps, a wei at a time out of the pool. Newton converges from above on this
convex function, so ceiling division restores the one-sidedness the proof
depends on. After: zero losses, 19,847 gains.
math returned every result through padTo32, which keeps only the low 32 bytes.
MulDiv(2^255, 4, 1) returned 0. MulDiv(max, max, 1) returned 1. And dex.MulDiv
PANICS on the same input -- two behaviours for one operation, one of them a
plausible-looking wrong number in the primitive that computes fees and share
ratios. Now refuses with ErrOverflow, matching FullMath.sol. Consensus-visible;
it needs a coordinated upgrade.
Coverage: dex 57.1 -> 99.1, stableswap 80.6 -> 98.6, swap 87.6 -> 99.6,
v3 78.1 -> 98.7, math 78.5 -> 97.6. 50 of 52 mutations caught, both survivors
proven unreachable rather than assumed. dex is now order-independent: -count=2
and -shuffle=on both pass, 843 tests run individually and 260 shuffle seeds
clean. The leak was a package-level resolver latch that installed on top of
whatever was live; t.Cleanup had fixed the exit and not the entry.
Also corrected five comments describing the CLOB price limit as IEEE-754
float64 bits. It is exact big.Int on an integer grid, and a reviewer would have
believed consensus compared float bit patterns.
zeekay