From 2bf63f4c33e8fa3815cca74e03760eb23f17a7c0 Mon Sep 17 00:00:00 2001
From: Gabor Buella <gabor.buella@intel.com>
Date: Sat, 2 Feb 2019 07:33:55 +0100
Subject: [PATCH] Fix std::abs usage in memory_optimize_pass.cc (#15627)

test=develop

size_t is an unsigned integer, with a conversion rank
 larger than int, therefore in the following expression
 the int value was promoted to size_t, making it a
 subtraction of unsigned values. The result of such
 a subtraction is also an unsigned value.
---
 .../inference/analysis/passes/memory_optimize_pass.cc      | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/paddle/fluid/inference/analysis/passes/memory_optimize_pass.cc b/paddle/fluid/inference/analysis/passes/memory_optimize_pass.cc
index 3d1be9196fd..4b0a9d9b1c4 100644
--- a/paddle/fluid/inference/analysis/passes/memory_optimize_pass.cc
+++ b/paddle/fluid/inference/analysis/passes/memory_optimize_pass.cc
@@ -18,6 +18,7 @@
 #include <limits>
 #include <map>
 #include <string>
+#include <type_traits>
 #include <utility>
 #include <vector>
 #include "paddle/fluid/framework/ir/graph_helper.h"
@@ -168,7 +169,11 @@ bool FindSuitableTensorToReuse(
     if (!cluster->count(candidate)) continue;
 
     size_t space = space_table.at(candidate);
-    size_t space_diff = std::abs<size_t>(space - space_required);
+    PADDLE_ENFORCE(
+        space <= std::numeric_limits<std::make_signed<size_t>::type>::max(),
+        "space overload");
+    size_t space_diff =
+        std::abs((std::make_signed<size_t>::type)space - space_required);
     if (space_diff < best_fit.second) {
       best_fit.first = candidate;
       best_fit.second = space_diff;
-- 
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