I have attached two additional files:

output.genefi32.txt    output of grub-mkimage for EFI 32 bit

output.genbios.txt     output of grub-mkimage for non EFI

I noted that the __stack_chk_guard output entries are quite different in the EFI 32 bit versus the failing EFI 64 bit output.

In the non EFI output, the __stack_chk_guard entries do not appear at all.

(file #55497, file #55498)

I am testing the newly released version 2.12.

Using grub-mkimage.exe to create a bootable 64 bit EFI kernel.

When the kernel is loaded it gives message

symbol '_stack_chk_guard' not found

See the attached screenshot.
Then the kernel aborts.

I was extremely careful when generating the kernel to ensure that the matching libraries were used by the grub-mkimage command.
The libraries and command are all in the same directory, so it is very unlikely that a mismatch occurred.

This bug renders grub-2.12-for-windows useless.
The kernel will not boot.

I have also attached the Windows .bat script I used to generate the kernels.

Note: The 32 bit i386-efi and non EFI i386-pc kernels work fine.
The problem is strictly with the 64 bit x86_64-efi kernel.