What is run first inside a cout statement? (C++17)

Question

Say for example I have a long statement like

cout << findCurrent() << "," << findLowest() << "," << findHighest() << "," << findThird()<<"\n";

would findCurrent() be run before findLowest() like logic dictates?

Answer 1

Since C++17 the functions are guaranteed to be called left-to-right, i.e. findCurrent() is called first, then findLowest() and so on.

C++17 Standard references: [expr.shift]/4 (referring to the expression E1 << E2):

The expression E1 is sequenced before the expression E2.

[over.match.oper]/2: (describing overloaded operators)

the operands are sequenced in the order prescribed for the built-in operator.

[intro.execution]/15:

An expression X is said to be sequenced before an expression Y if every value computation and every side effect associated with the expression X is sequenced before every value computation and every side effect associated with the expression Y.

Link to cppreference summary

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Prior to C++17 the order of function calls was unspecified, meaning that they may be called in any order (and this order does not need to be the same on repeated invocations).