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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 - __builtin_object_size() handled inconsistently in latest git with scan-build"
href="https://bugs.llvm.org/show_bug.cgi?id=47993">47993</a>
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<th>Summary</th>
<td>__builtin_object_size() handled inconsistently in latest git with scan-build
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<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>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Static Analyzer
</td>
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<th>Assignee</th>
<td>dcoughlin@apple.com
</td>
</tr>
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<th>Reporter</th>
<td>tss@iki.fi
</td>
</tr>
<tr>
<th>CC</th>
<td>dcoughlin@apple.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>I upgraded to latest git version of clang yesterday:
clang version 12.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
5839e13910ca0d5ccd11debc0ea3f8491c8c29df)
And I started getting a bunch of warnings in my code base with scan-build (no
warnings with normal clang builds):
warning: Declared variable-length array (VLA) has negative size [core.VLASize]
This happens somewhat inconsistently. Below is the smallest test case I managed
to get to reproduce it:
#include <stdlib.h>
# define COMPILE_ERROR_IF_TRUE(condition) \
(sizeof(char[1 - 2 * ((condition) ? 1 : 0)]) - 1)
int extfunc(void);
static void func2(void)
{
char *d = malloc(10);
(void)COMPILE_ERROR_IF_TRUE(__builtin_object_size((d),1) < 10);
free(d);
if (extfunc() == 0)
extfunc();
}
void func1(void)
{
func2();
func2();
}
# scan-build clang test.c -c -o test.o
test.c:22:8: warning: Declared variable-length array (VLA) has negative size
[core.VLASize]
(void)COMPILE_ERROR_IF_TRUE(__builtin_object_size((d),1) < 10);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test.c:15:3: note: expanded from macro 'COMPILE_ERROR_IF_TRUE'
(sizeof(char[1 - 2 * ((condition) ? 1 : 0)]) - 1)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.</pre>
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