From 58c6f8c7f5e02ad396eb0e39fcf441bdb714ca1c Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Mon, 28 Oct 2019 14:30:56 -0700
Subject: [PATCH] Make unsigned-integer-overflow sanitizer happy (#1377)

---
 include/fmt/format.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index 41f9cc01..78660ab5 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1410,7 +1410,8 @@ template <typename Range> class basic_writer {
   template <typename Int> void write_decimal(Int value) {
     auto abs_value = static_cast<uint32_or_64_or_128_t<Int>>(value);
     bool is_negative = internal::is_negative(value);
-    if (is_negative) abs_value = 0 - abs_value;
+    // Don't do -abs_value since it trips unsigned-integer-overflow sanitizer.
+    if (is_negative) abs_value = ~abs_value + 1;
     int num_digits = internal::count_digits(abs_value);
     auto&& it =
         reserve((is_negative ? 1 : 0) + static_cast<size_t>(num_digits));