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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - CSA assumes illegal array access"
href="https://bugs.llvm.org/show_bug.cgi?id=41833">41833</a>
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<th>Summary</th>
<td>CSA assumes illegal array access
</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
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Static Analyzer
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<th>Assignee</th>
<td>dcoughlin@apple.com
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<th>Reporter</th>
<td>jhenry@grammatech.com
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<th>CC</th>
<td>dcoughlin@apple.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>I was expecting CSA to find an array-out-of-bounds error when dereferencing
s[1] in the following code:
-----------------
extern char *fcall();
static void example(buf, size, endp) char *buf;
int size;
char **endp;
{
register char *beg;
beg = buf+1;
// begin
beg = fcall();
if (beg != buf + 4) {
return;
}
// end
if (beg > buf && beg[-1] != '\n') {
char *s = "";
char c = s[1];
}
}
-----------------
In the above code, if we comment the lines between // begin and // end, the bug
is found because beg[-1] is safe.
However, if we have a call to an external function that changes the value of
beg, clang somehow assumes that beg[-1] is always incorrect (and consequently
stops the exploration of that path).
I've added an earlier check that makes sure beg == buf+4 but that did not help.
Is this the expected behavior?</pre>
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</p>
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