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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - False positive in for-loop in C: Analyzer says that loop needn't be executed, assert() preceding the loop is ignored"
href="http://llvm.org/bugs/show_bug.cgi?id=16541">16541</a>
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<th>Summary</th>
<td>False positive in for-loop in C: Analyzer says that loop needn't be executed, assert() preceding the loop is ignored
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>3.3
</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>
</tr>
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<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>
</tr>
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<th>Assignee</th>
<td>kremenek@apple.com
</td>
</tr>
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<th>Reporter</th>
<td>pspacek@redhat.com
</td>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
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<pre>Version:
clang 3.3rc3 (I used package clang-3.3-0.6.rc3.fc19.x86_64 in Fedora 19, i.e.
3.3rc3, source package is
<a href="http://kojipkgs.fedoraproject.org//packages/llvm/3.3/0.6.rc3.fc19/src/llvm-3.3-0.6.rc3.fc19.src.rpm">http://kojipkgs.fedoraproject.org//packages/llvm/3.3/0.6.rc3.fc19/src/llvm-3.3-0.6.rc3.fc19.src.rpm</a>)
Following function call generates false positive:
4290 CHECK(ldap_pool_getconnection(inst->pool, &conn));
← Within the expansion of the macro 'CHECK':
a Calling 'ldap_pool_getconnection'
b Returning from 'ldap_pool_getconnection'
4291
4292 /* Try to connect. */
4293 while (conn->handle == NULL) {
← Access to field 'handle' results in a dereference of a null pointer
(loaded from variable 'conn')
The called function contains for-loop and the assertion:
3504 #include <assert.h>
3505
3506 static isc_result_t
3507 ldap_pool_getconnection(ldap_pool_t *pool, ldap_connection_t ** conn)
3508 {
3509 ldap_connection_t *ldap_conn = NULL;
3510 unsigned int i;
3511 isc_result_t result;
3512
3513 REQUIRE(pool != NULL);
3514 REQUIRE(conn != NULL && *conn == NULL);
3515 assert(pool->connections > 0);
← Within the expansion of the macro 'assert':
(seriously, there is nothing after the colon!)
3516
3517 ldap_conn = *conn;
← Null pointer value stored to 'ldap_conn'
3518 CHECK(semaphore_wait_timed(&pool->conn_semaphore));
← Within the expansion of the macro 'CHECK':
Assuming 'result' is equal to 0
3519 for (i = 0; i < pool->connections; i++) {
← Loop condition is false. Execution continues on line 3525
3520 ldap_conn = pool->conns[i];
3521 if (isc_mutex_trylock(&ldap_conn->lock) == ISC_R_SUCCESS)
3522 break;
3523 }
3524
3525 RUNTIME_CHECK(ldap_conn != NULL);
3526
3527 *conn = ldap_conn;
← Null pointer value stored to 'conn'
3528
3529 cleanup:
3530 if (result != ISC_R_SUCCESS) {
← Taking false branch
3531 log_error("timeout in ldap_pool_getconnection(): try to raise "
3532 "'connections' parameter; potential deadlock?");
3533 }
3534 return result;
3535 }
You can compile
<a href="https://fedorahosted.org/released/bind-dyndb-ldap/bind-dyndb-ldap-3.4.tar.bz2">https://fedorahosted.org/released/bind-dyndb-ldap/bind-dyndb-ldap-3.4.tar.bz2</a>
yourself and see the bug in natura.</pre>
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