From f2591397f92fe911257bef216b87bb2f233efb89 Mon Sep 17 00:00:00 2001
From: Lars Kanis <lars@greiz-reinsdorf.de>
Date: Fri, 5 Jun 2020 19:41:22 +0200
Subject: [PATCH 1/3] Revert to msvcrt.dll as LIBC on MINGW

ffi-1.13.0 switched FFI::Library::LIBC from msvcrt.dll to ucrtbase.dll
as part of #779 in commit c67468366e63bcf84512837384049fbba7e4748c .

As described in #788 ucrtbase.dll has behavioural changes which
shouldn't be released as part of a minor version change of ffi.
While the change makes sense for mswin, we revert it for mingw.

Fixes #788
---
 lib/ffi/platform.rb | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/ffi/platform.rb b/lib/ffi/platform.rb
index 959a72cff..ebc9d8b1c 100644
--- a/lib/ffi/platform.rb
+++ b/lib/ffi/platform.rb
@@ -129,7 +129,11 @@ def self.is_os(os)
     end
 
     LIBC = if IS_WINDOWS
-      "ucrtbase.dll"
+      if RbConfig::CONFIG['host_os'] =~ /mingw/i
+        RbConfig::CONFIG['RUBY_SO_NAME'].split('-')[-2] + '.dll'
+      else
+        "ucrtbase.dll"
+      end
     elsif IS_GNU
       GNU_LIBC
     elsif OS == 'cygwin'

From 90f4fcabc2ee729bfac83a103dac0780c37f05fd Mon Sep 17 00:00:00 2001
From: Lars Kanis <lars@greiz-reinsdorf.de>
Date: Tue, 9 Jun 2020 15:20:36 +0200
Subject: [PATCH 2/3] Revert usage of libc's time() on MINGW

Since libc is reverted to msvcrt.dll, we can use classic time() function again.
---
 bench/bench_time.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/bench/bench_time.rb b/bench/bench_time.rb
index 67148460e..aaec64f36 100644
--- a/bench/bench_time.rb
+++ b/bench/bench_time.rb
@@ -4,7 +4,7 @@ module BenchTime
   module Posix
     extend FFI::Library
     ffi_lib FFI::Library::LIBC
-    if FFI::Platform.windows?
+    if RUBY_PLATFORM =~ /mswin/
       attach_function :time, :_time64, [ :buffer_out ], :uint64, ignore_error: true
     else
       attach_function :time, [ :buffer_out ], :ulong, ignore_error: true

From f2d35a96a0cf639b7a603533323ef702c84c00ac Mon Sep 17 00:00:00 2001
From: Lars Kanis <lars@greiz-reinsdorf.de>
Date: Tue, 9 Jun 2020 15:53:00 +0200
Subject: [PATCH 3/3] Add a spec regarding issue #788

---
 spec/ffi/library_spec.rb | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/spec/ffi/library_spec.rb b/spec/ffi/library_spec.rb
index ff18f9b71..b622a29ac 100644
--- a/spec/ffi/library_spec.rb
+++ b/spec/ffi/library_spec.rb
@@ -64,6 +64,20 @@ class StructUCDP < FFI::Struct
     end
   end
 
+  if RbConfig::CONFIG['host_os'] =~ /mingw/
+    # See https://github.com/ffi/ffi/issues/788
+    it "libc functions shouldn't call an invalid parameter handler" do
+      mod = Module.new do
+        extend FFI::Library
+        ffi_lib 'c'
+        attach_function(:get_osfhandle, :_get_osfhandle, [:int], :intptr_t)
+      end
+
+      expect( mod.get_osfhandle(42) ).to eq(-1)
+    end
+  end
+
+
   describe "ffi_lib" do
     it "empty name list should raise error" do
       expect {