Using result of comma operator as l-value is not valid in C. But in C++, result of comma operator can be used as l-value if the right operand of the comma operator is l-value.
For example, if we compile the following program as a C++ program, then it works and prints b = 30. And if we compile the same program as C program, then it gives warning/error in compilation (Warning in Dev C++ and error in Code Blocks).
b = 30
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