Creating symbols from invalid Unicode characters causes segfault

[jiahao]

I was trying to trap #5712 by autogenerating a bunch of variables with unicode names, and came across this segfault:

julia> symbol(char(0xdcdb))

Program received signal SIGSEGV, Segmentation fault.
0x000000010012f263 in fl_raise ()
(gdb) bt
#0  0x000000010012f263 in fl_raise ()
#1  0x000000010012f3e0 in lerrorf ()
#2  0x000000010012fb4f in symbol ()
#3  0x0000000100068ce9 in julia_to_scm (v=0x101156a80) at ast.c:378
#4  0x000000010006b8d4 in array_to_list (a=0x1024a8d40) at ast.c:358
#5  0x0000000100068daa in julia_to_scm (v=0x1024aea20) at ast.c:391
#6  0x000000010006b8d4 in array_to_list (a=0x1024a8d80) at ast.c:358
#7  0x0000000100068daa in julia_to_scm (v=0x1024aea40) at ast.c:391
#8  0x000000010006983b in jl_expand (expr=0x1024aea40) at ast.c:506
#9  0x0000000100120f0c in jl_toplevel_eval_flex (e=0x1024aea40, fast=1) at toplevel.c:432
#10 0x0000000100121c98 in jl_toplevel_eval (v=0x1024aea40) at toplevel.c:493
#11 0x000000010006e6ad in jl_f_top_eval (F=0x10196fb80, args=0x7fff5fbfef98, nargs=2) at builtins.c:377
#12 0x0000000102bad7ed in julia_eval_user_input14869 ()
#13 0x0000000102badaf1 in jlcall_julia_eval_user_input14869 ()
#14 0x00000001000643e8 in jl_apply_generic (F=0x1042ab1e0, args=0x7fff5fbff180, nargs=2) at gf.c:1372
#15 0x0000000102ba4728 in julia_run_repl14618 ()

Note that 0xdcdb is a valid Unicode code point, but an invalid Unicode character.

[JeffBezanson]

Ah, this is because it didn't used to be possible for creating a symbol to raise errors. Now it can raise a normalization error.