From 91e425587a0b9b5ac0d1005844c661fee2e2813b Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Tue, 27 Aug 2024 21:34:44 -0700
Subject: [PATCH] Avoid `rand()` in the legacy `tr1` test suite (#4921)

---
 tests/tr1/tests/algorithm/test.cpp | 18 +++++++++++-------
 tests/tr1/tests/memory2/test.cpp   |  6 ++++--
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/tests/tr1/tests/algorithm/test.cpp b/tests/tr1/tests/algorithm/test.cpp
index 78683be089..ca9ee9c9d3 100644
--- a/tests/tr1/tests/algorithm/test.cpp
+++ b/tests/tr1/tests/algorithm/test.cpp
@@ -11,6 +11,7 @@
 #include <algorithm>
 #include <ctype.h>
 #include <functional>
+#include <random>
 #include <string.h>
 
 // FUNCTION OBJECTS
@@ -294,15 +295,13 @@ void test_copy(char* first, char* last, char* dest) { // test copying template f
     CHECK_STR(array2, "aaxx");
 }
 
-CSTD size_t frand(CSTD size_t nmax) { // return random value in [0, nmax)
-    return CSTD rand() % nmax;
-}
-
 struct rand_gen { // uniform random number generator
+    STD mt19937 mt;
+
     typedef CSTD size_t result_type;
 
     result_type operator()() { // get random value
-        return CSTD rand() & 0xfffff;
+        return mt() & 0xfffff;
     }
 
     static result_type(min)() { // get minimum value
@@ -429,8 +428,13 @@ void test_mutate(char* first, char* last, char* dest) { // test mutating templat
     CHECK_STR(array, "ebgf");
 
     STD random_shuffle(first, last);
-    CSTD size_t (*prand)(CSTD size_t) = &frand;
-    STD random_shuffle(first, last, prand);
+
+    STD mt19937 mt;
+    auto rng_func = [&mt](CSTD size_t nmax) { // return random value in [0, nmax)
+        STD uniform_int_distribution<CSTD size_t> dist{0, nmax - 1};
+        return dist(mt);
+    };
+    STD random_shuffle(first, last, rng_func);
 
     rand_gen urng;
     STD shuffle(first, last, urng);
diff --git a/tests/tr1/tests/memory2/test.cpp b/tests/tr1/tests/memory2/test.cpp
index c03407804a..99e2ff3bf6 100644
--- a/tests/tr1/tests/memory2/test.cpp
+++ b/tests/tr1/tests/memory2/test.cpp
@@ -7,7 +7,7 @@
 #include "tdefs.h"
 #include <memory>
 #include <mutex>
-#include <stdlib.h>
+#include <random>
 #include <thread>
 #include <vector>
 
@@ -15,6 +15,7 @@ using STD shared_ptr;
 using STD weak_ptr;
 
 using STD lock_guard;
+using STD mt19937;
 using STD mutex;
 using STD thread;
 using STD vector;
@@ -27,6 +28,7 @@ static shared_ptr<int> sp;
 static mutex start_mtx;
 
 static void ctors() { // construct a gazillion shared and weak pointers
+    mt19937 mt;
 
     { // wait for access
         lock_guard<mutex> lock(start_mtx);
@@ -34,7 +36,7 @@ static void ctors() { // construct a gazillion shared and weak pointers
 
     for (int i = 0; i < NSETS; ++i) {
         for (int j = 0; j < NREPS; ++j) {
-            if (rand() % 2 != 0) {
+            if (mt() % 2 != 0) {
                 shared_ptr<int> sp0(sp);
             } else {
                 weak_ptr<int> wp0(sp);