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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 - [C++20] [Module] The combination of iostream and file with .cppm suffix would crash"
href="https://bugs.llvm.org/show_bug.cgi?id=52531">52531</a>
</td>
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<tr>
<th>Summary</th>
<td>[C++20] [Module] The combination of iostream and file with .cppm suffix would crash
</td>
</tr>
<tr>
<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>All
</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>
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<th>Component</th>
<td>C++2a
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>yedeng.yd@linux.alibaba.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
</tr></table>
<p>
<div>
<pre>I met an interesting bug which would happen only if iosstream and module file
end with `.cppm`.
Here is the reproducer:
```C++
// Hello.cppm
module;
#include <iostream>
export module Hello;
export void SayHello()
{
std::cout << "Hello World.\n";
}
// main.cpp
import Hello;
int main() {
SayHello();
return 0;
}
```
And if I compile it as:
```
clang++ -std=c++20 --precompile Hello.cppm -o Hello.pcm
clang++ -std=c++20 -fprebuilt-module-path=. Hello.pcm main.cpp
```
And the generated executable would crash.
Interestingly, it wouldn't crash if we use `std::printf` instead of `std::cout`
```C++
// Hello.cppm
module;
#include <cstdio>
export module Hello;
export void SayHello()
{
std::printf("Hello World.\n");
}
// main.cpp
import Hello;
int main() {
SayHello();
return 0;
}
```
Also, it wouldn't crash if the suffix is `cpp` instead of `cppm`. For example:
```C++
// Hello.cpp
module;
#include <iostream>
export module Hello;
export void SayHello()
{
std::cout << "Hello World.\n";
}
// main.cpp
import Hello;
int main() {
SayHello();
return 0;
}
```
Compile argument:
```
clang++ -std=c++20 -Xclang -emit-module-interface Hello.cpp -o Hello.pcm
clang++ -std=c++20 -fprebuilt-module-path=. say_hello.cpp main.cpp
```
I am not sure if this is a bug in compiler or in runtime. It is appreciate if
someone could help to confirm this.</pre>
</div>
</p>
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