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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Missing diagnostics about unsequenced modifications and unintentional assignments"
href="https://bugs.llvm.org/show_bug.cgi?id=34363">34363</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Missing diagnostics about unsequenced modifications and unintentional assignments
</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>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Frontend
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>hans@chromium.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Some interesting cases from a Chromium bug report:
<a href="https://bugs.chromium.org/p/chromium/issues/detail?id=760070">https://bugs.chromium.org/p/chromium/issues/detail?id=760070</a>
$ cat /tmp/a.cc
void f(int x, int y) {
bool b = (x == y) ? 42 : b = 43;
bool c = c = y == 42;
}
$ bin/clang -c -Weverything /tmp/a.cc
/tmp/a.cc:1:6: warning: no previous prototype for function 'f'
[-Wmissing-prototypes]
void f(int x, int y) {
^
1 warning generated.
$ gcc -c -Wall /tmp/a.cc
/tmp/a.cc: In function ‘void f(int, int)’:
/tmp/a.cc:2:32: warning: operation on ‘b’ may be undefined [-Wsequence-point]
bool b = (x == y) ? 42 : b = 43;
^
/tmp/a.cc:4:21: warning: operation on ‘c’ may be undefined [-Wsequence-point]
bool c = c = y == 42;
^
Sequence points aside, perhaps it would make sense to warn (and suggest
parenthesis) about the right-hand side assignment like we do in if-statements?
$ cat /tmp/a.cc
bool f(int x, int y) {
bool b = x = y;
return b;
}
$ bin/clang -c -Weverything /tmp/a.cc
/tmp/a.cc:1:6: warning: no previous prototype for function 'f'
[-Wmissing-prototypes]
bool f(int x, int y) {
^
1 warning generated.</pre>
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