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From: "prasoonsaurav.nit at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/51836] New: -Wsequence-point fails when convoluted expressions with multiple side effects are used (C++03) Date: Thu, 12 Jan 2012 09:11:00 -0000 [thread overview] Message-ID: <bug-51836-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51836 Bug #: 51836 Summary: -Wsequence-point fails when convoluted expressions with multiple side effects are used (C++03) Classification: Unclassified Product: gcc Version: 4.4.6 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassigned@gcc.gnu.org ReportedBy: prasoonsaurav.nit@gmail.com Consider the following example int main() { int i=10; i += (i , i++, i) + i; // also invokes UB } prasoon@Prasoon:~/test_code$ cat ub.cpp int main() { int i=10; i += (i , i++, i) + i; // also invokes UB } prasoon@Prasoon:~/test_code$ g++ -Wsequence-point ub.cpp prasoon@Prasoon:~/test_code$ I don't get any warning like 'operation on 'i' may be undefined. Another similar example int main() { char *str; char array[100]= "Hello"; if((str = array)[0] == 'H'){ //do something } } As per my understanding (str = array)[0] also invokes UB but no warning is given by g++ even after using that option. Another example is int main() { int a = 10; ++a = 100; // UB }
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