util: Avoid invalid integer negation in FormatMoney: make FormatMoney(const CAmount& n) well-defined also when n is std::numeric_limits<CAmount>::min()

2 files changed, 9 insertions, 5 deletions

diff --git a/src/util/moneystr.cpp b/src/util/moneystr.cpp
index 1bc8d02eab..3f9ce7dce4 100644
--- a/src/util/moneystr.cpp
+++ b/src/util/moneystr.cpp
@@ -9,13 +9,17 @@
 #include <util/strencodings.h>
 #include <util/string.h>
 
-std::string FormatMoney(const CAmount& n)
+std::string FormatMoney(const CAmount n)
 {
     // Note: not using straight sprintf here because we do NOT want
     // localized number formatting.
-    int64_t n_abs = (n > 0 ? n : -n);
-    int64_t quotient = n_abs/COIN;
-    int64_t remainder = n_abs%COIN;
+    static_assert(COIN > 1);
+    int64_t quotient = n / COIN;
+    int64_t remainder = n % COIN;
+    if (n < 0) {
+        quotient = -quotient;
+        remainder = -remainder;
+    }
     std::string str = strprintf("%d.%08d", quotient, remainder);
 
     // Right-trim excess zeros before the decimal point:
diff --git a/src/util/moneystr.h b/src/util/moneystr.h
index da7f673cda..2aedbee358 100644
--- a/src/util/moneystr.h
+++ b/src/util/moneystr.h
@@ -17,7 +17,7 @@
 /* Do not use these functions to represent or parse monetary amounts to or from
  * JSON but use AmountFromValue and ValueFromAmount for that.
  */
-std::string FormatMoney(const CAmount& n);
+std::string FormatMoney(const CAmount n);
 /** Parse an amount denoted in full coins. E.g. "0.0034" supplied on the command line. **/
 [[nodiscard]] bool ParseMoney(const std::string& str, CAmount& nRet);