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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - std::shuffle() hangs with clang but works well with gcc/msvs"
href="https://bugs.llvm.org/show_bug.cgi?id=49621">49621</a>
</td>
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<th>Summary</th>
<td>std::shuffle() hangs with clang but works well with gcc/msvs
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>yury.norov@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, mikkqu@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>Confirmed on Linux and Mac. Discovered with Michail Kalashnikov.
clang -v
Apple clang version 12.0.0 (clang-1200.0.32.29)
Target: x86_64-apple-darwin20.3.0
Thread model: posix
InstalledDir: /Applications/
Reproducer: <a href="https://rextester.com/ZMML24952">https://rextester.com/ZMML24952</a>
#include <iostream>
#include <vector>
#include <algorithm>
#include <random>
using namespace std;
int shuffler_fn(int i) {
//cout << "Shuffler: " << i << endl;
return std::rand() % i;
}
void random_shuffle() {
vector<int> rows{1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
std::random_shuffle(rows.begin(), rows.end(), shuffler_fn);
for (const auto& item : rows) {
cout << item << ' ';
}
}
class Shuffler {
public:
typedef int result_type;
static constexpr int min() { return 0; }
static constexpr int max() { return RAND_MAX; }
int operator()() const { return std::rand(); }
};
void just_shuffle() {
vector<int> rows{1, 2, 3, 4, 5, 6, 7, 8, 9, 0};
Shuffler shuffler;
std::shuffle(rows.begin(), rows.end(), shuffler);
for (const auto& item : rows) {
cout << item << ' ';
}
}
int main()
{
random_shuffle();
cout << endl;
just_shuffle();
cout << endl;
return 0;
}</pre>
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