X-Git-Url: http://bilbo.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/3a1ea70a418f393ca1677074e928c664022295bd..f9b13d923d31bb0336aeeaab6d5b7ba33812f3f7:/src/xbt/random.cpp

diff --git a/src/xbt/random.cpp b/src/xbt/random.cpp
index 5160ba3c7f..449207c9bb 100644
--- a/src/xbt/random.cpp
+++ b/src/xbt/random.cpp
@@ -1,4 +1,4 @@
-/* Copyright (c) 2019-2020. The SimGrid Team. All rights reserved.               */
+/* Copyright (c) 2019-2022. The SimGrid Team. All rights reserved.               */
 
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
@@ -65,14 +65,22 @@ double StdRandom::normal(double mean, double sd)
 
 int XbtRandom::uniform_int(int min, int max)
 {
-  unsigned long range  = max - min + 1;
+  // The casts to unsigned are here to ensure that the value of range is correctly calculated, even when greater than
+  // INT_MAX.  See the corresponding unit tests for examples.
+  unsigned long range = static_cast<unsigned>(max) - static_cast<unsigned>(min);
   xbt_assert(min <= max,
              "The minimum value for the uniform integer distribution must not be greater than the maximum value");
-  xbt_assert(range > 0, "Overflow in the uniform integer distribution, please use a smaller range.");
+  xbt_assert(range <= decltype(mt19937_gen)::max(),
+             "Overflow in the uniform integer distribution, please use a smaller range.");
+  if (range == decltype(mt19937_gen)::max())
+    return static_cast<int>(mt19937_gen() + min);
+
+  ++range;
+  unsigned long limit = decltype(mt19937_gen)::max() - decltype(mt19937_gen)::max() % range;
   unsigned long value;
   do {
     value = mt19937_gen();
-  } while (value >= decltype(mt19937_gen)::max() - decltype(mt19937_gen)::max() % range);
+  } while (value >= limit);
   return static_cast<int>(value % range + min);
 }