FFI 0.13.0 no longer ignores invalid parameters

[joshcooper]

The ffi 0.13.0 release on Windows switched to using the universal C runtime instead of msvcrt in https://github.com/ffi/ffi/pull/779/files#diff-db0e38803c251431bdf21ae8936ac3f6L132-R132. Previously, msvcrt ignored invalid parameters, but ucrtbase will abort by default

Many functions now validate their parameters, halting execution if given invalid parameters. This validation may break code that passes invalid parameters and relies on the function ignoring them or just returning an error code.

This can be demonstrated using:

require 'ffi'

module MSVCRT
  extend FFI::Library
  ffi_lib 'msvcrt'
  attach_function(:get_osfhandle, :_get_osfhandle, [:int], :intptr_t)
end

module UCRTBASE
  extend FFI::Library
  ffi_lib 'ucrtbase'
  attach_function(:get_osfhandle, :_get_osfhandle, [:int], :intptr_t)
end

puts "msvcrt"
puts MSVCRT.get_osfhandle(42)
puts "ucrtbase"
puts UCRTBASE.get_osfhandle(42)
# we never get here
puts "Done"

Note that "Done" is never printed:

C:\Users\josh>bundle exec ruby osf.rb
msvcrt
-1
ucrtbase

This isn't a problem with FFI, but the ruby process aborts with 0xc0000409 without any output, which makes debugging the problem difficult. It'd be great to mention the behavior change in the release notes, and perhaps describe how to install an error handler so that the application can decide how to handle the exception: https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/set-invalid-parameter-handler-set-thread-local-invalid-parameter-handler?view=vs-2019.

[larskanis]

@joshcooper Thank you for your great analysis!

Obviously the change of FFI::Library::LIBC has an impact to several gems and the crashes are more due to the described behavioral change than due to a bug in the depending gem. This behavioral change wasn't intended by a minor version bump (from ffi-1.12 to 1.13). Maybe this is something for ffi-2.0, but for now I think it's best to revert to msvcrt.dll for the time being and release it as ffi-1.13.1 soon.

[joshcooper]

Thanks @larskanis, much appreciated!