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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 - clang-cl does not automatically convert a non-capturing lambda to a function pointer with a specific calling convention"
href="https://bugs.llvm.org/show_bug.cgi?id=38285">38285</a>
</td>
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<th>Summary</th>
<td>clang-cl does not automatically convert a non-capturing lambda to a function pointer with a specific calling convention
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>-New Bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>jeroen.ketema@philips.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
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<div>
<pre>Created <span class=""><a href="attachment.cgi?id=20594" name="attach_20594" title="Source file with de code from the description">attachment 20594</a> <a href="attachment.cgi?id=20594&action=edit" title="Source file with de code from the description">[details]</a></span>
Source file with de code from the description
cl.exe allows for a non-capturing lambda to be converted to a function pointer
with any calling convention. For example, the following compiles with cl.exe.
```
<span class="quote">> type foo.cpp</span >
typedef int (__stdcall * FuncType)(int p);
FuncType func;
int main() {
func = [](int p) { return p + 1; };
return 0;
}
```
```
<span class="quote">> cl.exe foo.cpp</span >
Microsoft (R) C/C++ Optimizing Compiler Version 19.00.24215.1 for x86
Copyright (C) Microsoft Corporation. All rights reserved.
foo.cpp
Microsoft (R) Incremental Linker Version 14.00.24215.1
Copyright (C) Microsoft Corporation. All rights reserved.
/out:foo.exe
foo.obj
```
clang-cl does not allow this:
```
<span class="quote">> clang-cl.exe -m32 foo.cpp</span >
foo.cpp(6,10): error: assigning to 'FuncType' (aka 'int (*)(int)
__attribute__((stdcall))') from incompatible type
'(lambda at foo.cpp:6:10)'
func = [](int p) { return p + 1; };
^~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
```
For the official documentation see near the bottom of
<a href="https://msdn.microsoft.com/en-us/library/dd293608.aspx">https://msdn.microsoft.com/en-us/library/dd293608.aspx</a>: "Stateless lambdas,
which are omni-convertible to function pointers that use arbitrary calling
conventions."
Some more informal context here:
<a href="https://blogs.msdn.microsoft.com/oldnewthing/20150220-00/?p=44623">https://blogs.msdn.microsoft.com/oldnewthing/20150220-00/?p=44623</a></pre>
</div>
</p>
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