[Bug c++/51836] New: -Wsequence-point fails when convoluted expressions with multiple side effects are used (C++03)
prasoonsaurav.nit at gmail dot com
gcc-bugzilla@gcc.gnu.org
Thu Jan 12 09:11:00 GMT 2012
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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