how to find stack trace of "Error: 4invalid UTF-8 sequence" "Error: std.format int argument expected"?

[nobody]

dmd v1.045 on Linux, I got error like:

Error: 4invalid UTF-8 sequence
Error: std.format int argument expected

Then I run the program under debugger, there is no indication where the error
occurred:

Error: 4invalid UTF-8 sequence

Program exited with code 01.
(gdb) where
No stack.

This is ridiculous: why cannot the library generate segfault instead?