$ ../cpla.sh p100a
$ clang++ p100a.cpp -std=c++03 -Wall
p100a.cpp:24:12: warning: multiple unsequenced modifications to 'i' [-Wunsequenced]
int x = S(i=1) << (i=2);
           ^        ~
p100a.cpp:25:23: warning: multiple unsequenced modifications to 'j' [-Wunsequenced]
int y = operator<<(S(j=1), j=2);
                      ^     ~
2 warnings generated.
Assertion failed: (s == "I have heard it works only if you believe in it"), function f, file p100a.cpp, line 15.
../cpla.sh: line 6: 14184 Abort trap: 6           ./$1l03 $2
$ clang++ p100a.cpp -std=c++2a -Wall
p100a.cpp:24:12: warning: multiple unsequenced modifications to 'i' [-Wunsequenced]
int x = S(i=1) << (i=2);
           ^        ~
p100a.cpp:25:23: warning: multiple unsequenced modifications to 'j' [-Wunsequenced]
int y = operator<<(S(j=1), j=2);
                      ^     ~
2 warnings generated.
Assertion failed: (s == "I have heard it works only if you believe in it"), function f, file p100a.cpp, line 15.
../cpla.sh: line 11: 14188 Abort trap: 6           ./$1l2a $2

$ g++-8 p100a.cpp -std=c++03  -Wall
p100a.cpp: In function 'void __static_initialization_and_destruction_0(int, int)':
p100a.cpp:24:21: warning: operation on 'i' may be undefined [-Wsequence-point]
 int x = S(i=1) << (i=2);
                   ~~^~~
p100a.cpp:25:29: warning: operation on 'j' may be undefined [-Wsequence-point]
 int y = operator<<(S(j=1), j=2);
                            ~^~
Assertion failed: (s == "I have heard it works only if you believe in it"), function f, file p100a.cpp, line 15.
../cpla.sh: line 17: 14197 Abort trap: 6           ./$1g03 $2

$ g++-8 p100a.cpp -std=c++2a  -Wall
p100a.cpp: In function 'void __static_initialization_and_destruction_0(int, int)':
p100a.cpp:24:21: warning: operation on 'i' may be undefined [-Wsequence-point]
 int x = S(i=1) << (i=2);
                   ~~^~~
p100a.cpp:25:29: warning: operation on 'j' may be undefined [-Wsequence-point]
 int y = operator<<(S(j=1), j=2);
                            ~^~
Assertion failed: (s == "I have heard it works only if you believe in it"), function f, file p100a.cpp, line 15.
../cpla.sh: line 23: 14206 Abort trap: 6           ./$1g2a $2