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[std-proposals] Ensuring safety of longjmp with [[trivial_dtors]]

From: Frederick Virchanza Gotham <cauldwell.thomas_at_[hidden]>
Date: Fri, 14 Apr 2023 09:07:14 +0100
In the latest Standard we have:

"The function signature longjmp(jmp_buf jbuf, int val) has more
restricted behavior in this document. A setjmp/longjmp call pair has
undefined behavior if replacing the setjmp and longjmp by catch and
throw would invoke any non-trivial destructors for any objects with
automatic storage duration. A call to setjmp or longjmp has undefined
behavior if invoked in a suspension context of a coroutine."

So let's say we have:

extern void Some_Library_Func( void (*)(void) );

jmp_buf jb;

void JumpBack(void)

int main(void)

    Some_Library_Func( JumpBack );

We would really want an assurance that the function,
Some_Library_Func, won't put an object on the stack that has a
non-trivial destructor. Maybe a function attribute could ensure this?

extern void SomeOtherFunc(void);

[[trivial_dtors]] void Some_Library_Func( void (*)(void) )
    std::string s; // COMPILER ERROR: cannot
                            // put an object with an non-trivial
                            // constructor on the stack

    SomeOtherFunc(); // COMPILER ERROR: cannot
                                    // call another function that has
                                    // not been marked as trivial_dtors

Received on 2023-04-14 08:07:26