Indicates that the variable or function parameter has an indeterminate value if it is not initialized.

[edit]Syntax

[edit]Explanation

[[indeterminate]] can be applied to the definition of a block variable with automaticstorage duration or to a declaration of a parameter of afunction declaration. The attribute specifies that the bytes comprising the storage of an object with automatic storage duration is initiallyindeterminate rather than erroneous.

If a function parameter is declared with[[indeterminate]], it must be declared in the first declaration of its function. If a function parameter is declared with[[indeterminate]] in the first declaration of its function in one translation unit and the same function is declared without[[indeterminate]] on the same parameter in its first declaration in another translation unit, the program isill-formed, no diagnostic required.

[edit]Notes

The[[indeterminate]] attribute restores the undefined behavior that was implicitly introduced until C++26. It may make compilers consider a code path reading an indeterminate value unreachable.

[edit]Example

void f(int); void g(){int x[[indeterminate]];// indeterminate valueint y;// erroneous value     f(x);// undefined behavior    f(y);// erroneous behavior} struct T{    T(){}int x;}; void h(T a[[indeterminate]], T b){    f(a.x);// undefined behavior when called below    f(b.x);// erroneous behavior when called below} h(T(), T());

[edit]References

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