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-rw-r--r--src/bignum.h10
1 files changed, 9 insertions, 1 deletions
diff --git a/src/bignum.h b/src/bignum.h
index 3716c49656..5190c2f390 100644
--- a/src/bignum.h
+++ b/src/bignum.h
@@ -131,7 +131,15 @@ public:
if (sn < (int64)0)
{
- n = -sn;
+ // We negate in 2 steps to avoid signed subtraction overflow,
+ // i.e. -(-2^63), which is an undefined operation and causes SIGILL
+ // when compiled with -ftrapv.
+ //
+ // Note that uint64_t n = sn, when sn is an int64_t, is a
+ // well-defined operation and n will be equal to sn + 2^64 when sn
+ // is negative.
+ n = sn;
+ n = -n;
fNegative = true;
} else {
n = sn;