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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::map operator< stack frame size consumption"
href="https://bugs.llvm.org/show_bug.cgi?id=34188">34188</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>std::map operator< stack frame size consumption
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</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>
<tr>
<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>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>lebedev.ri@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>This could be either expected, or be a libcxx implementation defect, or clang
missing optimization, or any combination of those.
Reduced testcase:
#include <map>
#include <memory>
#include <string>
struct a;
struct b
{
std::string c;
std::string f;
std::string d;
int operator<(b e) const
{
return tie(c, f, d) < tie(c, f, e.d);
}
};
struct j
{
std::map<b, std::unique_ptr<a> > cameras;
const a *g(const std::string &, const std::string &, const std::string &)
const;
};
using std::string;
inline b h(string, string, string)
{
b i;
return i;
}
const a *j::g(const string &c, const string &f, const string &d) const
{
auto camera = cameras.find(h(0, 0, 0));
return camera->second.get();
}
Compilation flags: -std=c++14 -c -Wframe-larger-than=0 cxx.cpp
Here is a comparison of stack frame size usage in function 'b::operator<':
/ --------------------------\
|======| libcxx | libstdc++ |
| -O3 | n/a | n/a |
| -O2 | n/a | n/a |
| -O1 | 72b | 88b |
| -O0 | 4840b | 88b |
| noop | 4840b | 88b |
\---------------------------/
The measurements were made with clang tip, libcxx tip (compiled in release
build mode, no sanitizations)</pre>
</div>
</p>
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