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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - gdb cannot break on function that has thunk"
href="https://bugs.llvm.org/show_bug.cgi?id=43760">43760</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>gdb cannot break on function that has thunk
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>9.0
</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>C++
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>manjian2006@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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</tr></table>
<p>
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<pre>```
#include <stdio.h>
class BaseClassOne {
public:
virtual void foo();
};
class BaseClassTwo {
public:
virtual void bar();
};
class DeriveClass: public BaseClassOne, BaseClassTwo {
public:
void foo() override;
void bar() override;
};
void BaseClassOne::foo() {
printf("This is BaseClassOne: %p\n", this);
}
void BaseClassTwo::bar() {
printf("This is BaseClassTwo: %p\n", this);
}
void DeriveClass::foo() {
printf("This is DeriveClass foo: %p\n", this);
}
void DeriveClass::bar() {
printf("This is DeriveClass bar: %p\n", this);
}
```
gdb can break on DeriveClass::bar， but not_ZThn8_N11DeriveClass3barEv。The
expression static_cast<BaseClassTwo*>(o)->bar() will not trigger the break
point, because thunk do function inline like the following show:
```
; Function Attrs: nounwind uwtable
define dso_local void @_ZThn8_N11DeriveClass3barEv(%class.DeriveClass*)
unnamed_addr #0 align 2 {
%2 = getelementptr inbounds %class.DeriveClass, %class.DeriveClass* %0, i64
-1, i32 1
%3 = bitcast %class.BaseClassTwo* %2 to %class.DeriveClass*
tail call void @_ZN11DeriveClass3barEv(%class.DeriveClass* %3)
ret void
}
; Function Attrs: nounwind uwtable
define dso_local void @_ZThn8_N11DeriveClass3barEv(%class.DeriveClass*)
unnamed_addr #0 align 2 {
%2 = getelementptr inbounds %class.DeriveClass, %class.DeriveClass* %0, i64
-1, i32 1
%3 = bitcast %class.BaseClassTwo* %2 to %class.DeriveClass*
%4 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([29 x i8],
[29 x i8]* @.str.3, i64 0, i64 0), %class.DeriveClass* %3) #2
ret void
```</pre>
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