Google broke a conditional statement that verifies passwords on Chrome OS

Re:Google broke a conditional statement that verifies passwo... by xmprt on Thursday July 22, 2021 @04:53PM (#27924186)

So instead of short circuiting like that code should when it uses &&, it instead makes an assumption about the first part of the boolean expression because otherwise the code would have undefined behavior?

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Re:Google broke a conditional statement that verifies passwo... by dataflow on Thursday July 22, 2021 @04:59PM (#27924249)

Yeah. More specifically, it just inserts whatever behavior it likes for the undefined scenario, which in this case is "the same behavior as in the defined scenario".

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Re:Google broke a conditional statement that verifies passwo... by ddalex on Friday July 23, 2021 @03:03AM (#27927996)

I am utterly confused. How would the compiler know that has_value() guarantees that the ->label dereferencing work, since this is a bitwise operation ?

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Re:Google broke a conditional statement that verifies passwo... by dataflow on Friday July 23, 2021 @03:06AM (#27928022)

I would imagine has_value is checking to see if a pointer is NULL, and -> is dereferencing that same pointer. When the optimizer sees the two together it realizes the former is useless.

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Re:Google broke a conditional statement that verifies passwo... by ddalex on Friday July 23, 2021 @06:43AM (#27929221)

by this logic the compiler would optimize any short-circuiting because it KNOWS the programmer WOULD NEVER deference an invalid pointer

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Re:Google broke a conditional statement that verifies passwo... by jhasse on Friday July 23, 2021 @08:55AM (#27930116)

no, & is not short-circuiting

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