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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Anonymous structs/unions can violate "Last member element" constraint on flexible arrays"
href="https://bugs.llvm.org/show_bug.cgi?id=46255">46255</a>
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<th>Summary</th>
<td>Anonymous structs/unions can violate "Last member element" constraint on flexible arrays
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>vaibhav@linux.ibm.com
</td>
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<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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<pre>Description:
In 'C' mode defining a struct containing 2 or more structs having flexible
arrays should result in 'gnu-variable-sized-type-not-at-end' warning getting
triggered as flexible arrays should always be at the end of the containing
struct.
However if the member struct elements are wrapped in an anonymous union or a
struct then clang erroneously ignores this violation.
Example:
Consider following struct definitions ( <a href="https://godbolt.org/z/7nnBGz">https://godbolt.org/z/7nnBGz</a> ):
struct A { int a; int b[]; };
struct B { int a; int b[]; };
struct C {
/* warning: field 'a' with variable sized type 'struct A' not at
* the end of a struct or class is a GNU extension
* [-Werror,-Wgnu-variable-sized-type-not-at-end]
*/
struct A a;
struct B b;
};
struct C_U {
/* No warning reported */
struct A a;
union {
struct B b;
};
};
struct C_S {
/* No warning reported */
struct A a;
struct {
struct B b;
};
};
struct C_SU {
/* No warning reported */
struct A a;
struct {
struct B b;
};
union {
struct A aa;
};
};
Exception:
This issue is not observed in 'C++' mode ( <a href="https://godbolt.org/z/3nNzap">https://godbolt.org/z/3nNzap</a> )</pre>
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