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<head>
<base href="http://llvm.org/bugs/" />
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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 --- - [-cxx-abi microsoft] Base class with zero width bitfield has improper layout"
href="http://llvm.org/bugs/show_bug.cgi?id=18170">18170</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[-cxx-abi microsoft] Base class with zero width bitfield has improper layout
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.majnemer@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>consider:
#if defined(__clang__) || defined(__GNUC__)
typedef __SIZE_TYPE__ size_t;
#endif
extern "C" int printf(const char *fmt, ...);
extern "C" void *memset(void *ptr, int value, size_t num);
static char buffer[419430400];
inline void *operator new(size_t, void *pv) { return pv; }
struct ClassName0 {
char : 0;
ClassName0() {
}
};
struct ClassName1: public ClassName0 {
char ClassName1FieldName0;
ClassName1() {
printf("ClassName1FieldName0 : %llu\n", (unsigned long
long)((size_t)&ClassName1FieldName0 - (size_t)buffer));
}
};
struct ClassName2: public virtual ClassName1, public ClassName0 {
float ClassName2FieldName0;
float ClassName2FieldName1;
ClassName2() {
printf("ClassName2FieldName0 : %llu\n", (unsigned long
long)((size_t)&ClassName2FieldName0 - (size_t)buffer));
printf("ClassName2FieldName1 : %llu\n", (unsigned long
long)((size_t)&ClassName2FieldName1 - (size_t)buffer));
}
};
struct ClassName3: public virtual ClassName2, public virtual ClassName1 {
bool ClassName3FieldName0;
long long ClassName3FieldName1;
ClassName3() {
printf("ClassName3FieldName0 : %llu\n", (unsigned long
long)((size_t)&ClassName3FieldName0 - (size_t)buffer));
printf("ClassName3FieldName1 : %llu\n", (unsigned long
long)((size_t)&ClassName3FieldName1 - (size_t)buffer));
}
};
static void test_layout(const char *class_name, size_t size_of_class, size_t
align_of_class) {
printf(" sizeof(%s): %Iu\n", class_name, size_of_class);
printf("__alignof(%s): %Iu\n", class_name, align_of_class);
}
template <typename Class>
static void init_mem() {
memset(buffer, 0xcc, sizeof(buffer));
new (buffer) Class;
}
#define test(Class) init_mem<Class>(), test_layout(#Class, sizeof(Class),
__alignof(Class))
int main() {
test(ClassName0);
test(ClassName1);
test(ClassName2);
test(ClassName3);
}
msvc:
sizeof(ClassName0): 1
__alignof(ClassName0): 1
ClassName1FieldName0 : 0
sizeof(ClassName1): 1
__alignof(ClassName1): 1
ClassName1FieldName0 : 12
ClassName2FieldName0 : 4
ClassName2FieldName1 : 8
sizeof(ClassName2): 13
__alignof(ClassName2): 4
ClassName1FieldName0 : 24
ClassName2FieldName0 : 36
ClassName2FieldName1 : 40
ClassName3FieldName0 : 8
ClassName3FieldName1 : 16
sizeof(ClassName3): 44
__alignof(ClassName3): 8
clang:
sizeof(ClassName0): 1
__alignof(ClassName0): 1
ClassName1FieldName0 : 0
sizeof(ClassName1): 1
__alignof(ClassName1): 1
ClassName1FieldName0 : 12
ClassName2FieldName0 : 4
ClassName2FieldName1 : 8
sizeof(ClassName2): 13
__alignof(ClassName2): 4
ClassName1FieldName0 : 24
ClassName2FieldName0 : 40
ClassName2FieldName1 : 44
ClassName3FieldName0 : 8
ClassName3FieldName1 : 16
sizeof(ClassName3): 48
__alignof(ClassName3): 8</pre>
</div>
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