Bug fix: Allocatable argument 'x' is not allocated #472

[14NGiestas]

There is a unreliable behaviour when dealing with negative size at runtime in GCC 11, this bug fix is addressing this issue.

program main
    implicit none
    real, allocatable :: x(:)

    x = compile_time()
    print*, allocated(x) ! T
    print*, size(x)      ! 0

    x = runtime(100)
    print*, allocated(x) ! T
    print*, size(x)      ! 100

    x = runtime(-100)
    print*, allocated(x) ! F -> this is a problem!
    print*, size(x)      ! 0

    x = runtime(0)
    print*, allocated(x) ! T
    print*, size(x)      ! 0

    x = fix_runtime(-100)
    print*, allocated(x) ! T
    print*, size(x)      ! 0

contains

    function compile_time() result(res)
        real :: res(-100)
    end function

    function runtime(n) result(res)
        integer, intent(in) :: n
        real :: res(n)
    end function

    function fix_runtime(n) result(res)
        integer, intent(in) :: n
        real :: res(merge(n, 0, n > 0))
    end function

end program

[jvdp1]

Thank you. The declaration should be also changed in stdlib_math.fypp.

[14NGiestas]

I believe I should guard the logspace as well, to avoid any further trouble.

[jvdp1]

Thank you for these changes.

[ejovo13]

Elegant solution. Thank you for reporting this and working to clean it up so quickly. I also appreciate the fact that through this bug's discussion I have learned about the intrinsic function merge and its use cases compared to the stdlib optval.

[ghost]

Looks good. Thank you for the fix.

[awvwgk]

Thanks for sharing. Looks good to me.

[14NGiestas]

Maybe this two should also be guarded.

[jvdp1]

Thank you @14NGiestas for this bug fix. I'll merge it.

Fixes #472