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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 - LLDB sometimes can't determine the dynamic type of an object if the program is compiled with fPIC"
href="https://bugs.llvm.org/show_bug.cgi?id=50685">50685</a>
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<th>Summary</th>
<td>LLDB sometimes can't determine the dynamic type of an object if the program is compiled with fPIC
</td>
</tr>
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<th>Product</th>
<td>lldb
</td>
</tr>
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<th>Version</th>
<td>12.0
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</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>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>lldb-dev@lists.llvm.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>officesamurai@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>jdevlieghere@apple.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>If I compile the following code with fPIC or fPIE:
===
#include <boost/asio/io_context.hpp>
#include <boost/asio/strand.hpp>
void foo(boost::asio::io_context& context)
{
boost::asio::io_context::strand s{context};
}
struct Base
{
virtual ~Base() {}
};
struct Derived: Base
{
Derived(int zzz) : zzz(zzz) {}
int zzz = 0;
};
int main()
{
Derived d{123};
Base* b = &d;
return 0;
}
===
and run it in lldb, "print b" will print:
(Base *) $0 = 0x00007fffffffdc58
But if I compile it without fPIC/fPIE, or modify the code slightly, e.g. by
commenting out the unused function "foo", I get the expected output:
(Derived *) $0 = 0x00007fffffffdc58
The behaviour doesn't depend on the compiler; I tried clang 11.0 and gcc-10.2
and the result was the same.
Since the code depends on boost, I'm attaching the preprocessed version too.
I compile it as follows:
$ clang++ -g -fPIC test_preproc_clang.cpp -o test -lpthread
Clang version:
Ubuntu clang version 11.0.0-2
LLDB version:
lldb version 12.0.0 (<a href="mailto:git@github.com">git@github.com</a>:llvm/llvm-project.git revision
d28af7c654d8db0b68c175db5ce212d74fb5e9bc)
clang revision d28af7c654d8db0b68c175db5ce212d74fb5e9bc
llvm revision d28af7c654d8db0b68c175db5ce212d74fb5e9bc
boost version: 1.73.0</pre>
</div>
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