From: Lucian Grijincu <lucian@fb.com>
Date: Wed, 11 May 2016 17:45:33 +0000 (-0700)
Subject: folly: ubsan: format: avoid UB in abs(-INT_MIN)
X-Git-Tag: 2016.07.26~248
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=b3c4aa79622e50dfd0507dc195bc3ee5ccc8b377;p=folly.git

folly: ubsan: format: avoid UB in abs(-INT_MIN)

Summary:
abs(-INT_MIN) is UB. Avoid it by first casting the number to
its unsigned equivalent and then negating that.

Reviewed By: yfeldblum

Differential Revision: D3280835

fbshipit-source-id: 40922d686173e6467e15d5a6dc2b62ad718349b5
---

diff --git a/folly/Format-inl.h b/folly/Format-inl.h
index 35c0298e..48125dc5 100644
--- a/folly/Format-inl.h
+++ b/folly/Format-inl.h
@@ -443,7 +443,7 @@ class FormatValue<
     char sign;
     if (std::is_signed<T>::value) {
       if (folly::is_negative(val_)) {
-        uval = static_cast<UT>(-val_);
+        uval = -static_cast<UT>(val_);
         sign = '-';
       } else {
         uval = static_cast<UT>(val_);