VM crashes on malformed paths on windows

[sigurdm]

Reproduction:

dart --version
Dart SDK version: 2.11.0-190.0.dev (dev) (Tue Oct 6 07:16:45 2020 -0700) on "windows_x64"
> dart --snapshot=abc /C:/abc.dart
===== CRASH =====
ExceptionCode=-1073741819, ExceptionFlags=0, ExceptionAddress=00007FF714ABFA40
version=2.11.0-190.0.dev (dev) (Tue Oct 6 07:16:45 2020 -0700) on "windows_x64"
pid=25376, thread=25712, isolate_group=(nil)(0000000000000000), isolate=(nil)(0000000000000000)
isolate_instructions=0, vm_instructions=7ff71460df70
Stack dump aborted because InitialRegisterCheck failed.

[aam]

Crashes on linux as well(slightly differently though)

╰─➤  out/DebugX64/dart --snapshot=abc  "#$%" 
../../runtime/bin/main.cc: 645: error: expected: script_uri != NULL
version=2.11.0-edge.753a562b880820767a9ce7a8edb269613c491108 (be) (Tue Oct 13 22:24:44 2020 -0700) on "linux_x64"
pid=3113242, thread=3113242, isolate_group=(nil)((nil)), isolate=(nil)((nil))
isolate_instructions=0, vm_instructions=558048cea700
  pc 0x00005580490e64dc fp 0x00007ffff43cb1f0 dart::Profiler::DumpStackTrace(void*)+0x7c
  pc 0x0000558048cea832 fp 0x00007ffff43cb2d0 dart::Assert::Fail(char const*, ...)+0x82
  pc 0x0000558048ccf7d3 fp 0x00007ffff43cb3a0 out/DebugX64/dart+0x1af57d3
  pc 0x0000558048ccecc4 fp 0x00007ffff43cb450 dart::bin::RunMainIsolate(char const*, dart::bin::CommandLineOptions*)+0x64
  pc 0x0000558048cd00aa fp 0x00007ffff43cb580 dart::bin::main(int, char**)+0x5fa
  pc 0x0000558048cd0ecd fp 0x00007ffff43cb5a0 main+0xd
-- End of DumpStackTrace
[1]    3113242 abort      out/DebugX64/dart --snapshot=abc "#$%"

[aam]

I imagine this being result of a212b75 that allowed for script_uri to remain unpopulated null, which later combines with presence of --snapshot option in dartdev-unexpected
fashion(https://github.com/dart-lang/sdk/blob/master/runtime/bin/main.cc#L1294). Hopefully @bkonyi can confirm.

[bkonyi]

Yup, that looks like it could cause the issue. I'll investigate.