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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Struct size is 0 even if the compiler emites "warning: struct has size 0 in C, size 1 in C++ [-Wc++-compat]""
href="https://llvm.org/bugs/show_bug.cgi?id=24711">24711</a>
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<th>Summary</th>
<td>Struct size is 0 even if the compiler emites "warning: struct has size 0 in C, size 1 in C++ [-Wc++-compat]"
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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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>
</tr>
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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
</td>
</tr>
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<th>Reporter</th>
<td>douglas_yung@playstation.sony.com
</td>
</tr>
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
</td>
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<th>Classification</th>
<td>Unclassified
</td>
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<p>
<div>
<pre>Consider the following code:
/*** test.c ***/
#include <stdio.h>
struct S {
char tmp[0];
};
struct T {
struct S v01;
struct S v02;
};
int main(void) {
printf("%lu\n", sizeof(struct S));
printf("%lu\n", sizeof(struct T));
return 0;
}
/*****/
If you compile this as a .c file on x64 linux targeting x64 linux, using
-Wc++-compat, you get the following warnings:
test.c:3:1: warning: struct has size 0 in C, size 1 in C++ [-Wc++-compat]
struct S {
^
test.c:7:1: warning: struct has size 0 in C, non-zero size in C++
[-Wc++-compat]
struct T {
^
But if rename the file to be .cpp and recompile, you find that both of those
warnings are not true. The size of both S and T are reported to be 0, which
does at least seem to be consistent with what gcc produces.</pre>
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