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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 - unordered_map accepts non const hasher functor"
href="https://bugs.llvm.org/show_bug.cgi?id=49194">49194</a>
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</tr>
<tr>
<th>Summary</th>
<td>unordered_map accepts non const hasher functor
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>Macintosh
</td>
</tr>
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<th>OS</th>
<td>MacOS X
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++11
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>anton.veselskyi@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>If I want to create a unordered_map with a custom hasher, I need to provide a
functor that accepts the Key as a 3rd template parameter.
On all other compilers functors operator() should accept a Key as a const
parameter, if it is not const code will not compile.
clang ignores this error.
INVALID CODE THAT SHOULD NOT COMPILED(allowing hasher to change Key object):
```
struct pizza_hasher
{
size_t operator()(std::set<std::string> &s) const
{
std::hash<std::string> string_hasher;
size_t res = 23;
for(const string &str : s)
res ^= string_hasher(str);
return res;
}
};
using Pizzas = std::unordered_map<std::set<std::string>, std::vector<int>,
pizza_hasher>;
```
reproduced on:
Apple clang version 12.0.0 (clang-1200.0.32.29)
EXPECTED RESULT:
compilation error
ACTUAL RESULT:
compilation OK
valid code as a reference:
```
struct pizza_hasher
{
size_t operator()(const std::set<std::string> &s) const
{
std::hash<std::string> string_hasher;
size_t res = 23;
for(const string &str : s)
res ^= string_hasher(str);
return res;
}
};
using Pizzas = std::unordered_map<std::set<std::string>, std::vector<int>,
pizza_hasher>;
```</pre>
</div>
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