And the Windows extension finally loads.

Rakefile

@@ -24,6 +24,13 @@ Rake::ExtensionTask.new('grpc_c', spec) do |ext|
   ext.lib_dir = File.join('src', 'ruby', 'lib', 'grpc')
   ext.cross_compile = true
   ext.cross_platform = ['x86-mingw32', 'x64-mingw32']
+  ext.cross_compiling do |spec|
+    spec.files = %w( etc/roots.pem grpc_c.32.ruby grpc_c.64.ruby )
+    spec.files += Dir.glob('src/ruby/bin/**/*')
+    spec.files += Dir.glob('src/ruby/ext/**/*')
+    spec.files += Dir.glob('src/ruby/lib/**/*')
+    spec.files += Dir.glob('src/ruby/pb/**/*')
+  end
 end
 
 # Define the test suites

src/ruby/ext/grpc/extconf.rb

@@ -54,6 +54,8 @@
   LIBDIR
 ]
 
+windows = RUBY_PLATFORM =~ /mingw|mswin/
+
 grpc_root = File.expand_path(File.join(File.dirname(__FILE__), '../../../..'))
 
 grpc_config = ENV['GRPC_CONFIG'] || 'opt'
@@ -64,27 +66,16 @@
   grpc_lib_dir = File.join(grpc_root, 'libs', grpc_config)
 end
 
-unless File.exist?(File.join(grpc_lib_dir, 'libgrpc.a'))
+unless File.exist?(File.join(grpc_lib_dir, 'libgrpc.a')) or windows
   for var in %w( CC AR ) do
     ENV[var] = RbConfig::CONFIG[var]
   end
 
   ENV['LD'] = ENV['CC']
 
-  if RUBY_PLATFORM =~ /mingw|mswin/
-    ENV['SYSTEM'] = 'MINGW32'
-  end
-
   ENV['EMBED_OPENSSL'] = 'true'
   ENV['EMBED_ZLIB'] = 'true'
 
-  grpc_cppflags = ''
-  grpc_cppflags << ' -D_WIN32_WINNT=0x600 '
-  grpc_cppflags << ' -DUNICODE '
-  grpc_cppflags << ' -D_UNICODE '
-
-  ENV['CPPFLAGS'] = grpc_cppflags
-
   output_dir = File.expand_path(RbConfig::CONFIG['topdir'])
   grpc_lib_dir = File.join(output_dir, 'libs', grpc_config)
   ENV['BUILDDIR'] = output_dir
@@ -95,7 +86,7 @@
 end
 
 $CFLAGS << ' -I' + File.join(grpc_root, 'include')
-$LDFLAGS << ' ' + File.join(grpc_lib_dir, 'libgrpc.a')
+$LDFLAGS << ' ' + File.join(grpc_lib_dir, 'libgrpc.a') unless windows
 if grpc_config == 'gcov'
   $CFLAGS << ' -O0 -fprofile-arcs -ftest-coverage'
   $LDFLAGS << ' -fprofile-arcs -ftest-coverage -rdynamic'
@@ -108,11 +99,6 @@
 $CFLAGS << ' -Werror '
 $CFLAGS << ' -Wno-format '
 
-case RUBY_PLATFORM
-when /mingw|mswin/
-  $LDFLAGS << ' -static '
-end
-
 output = File.join('grpc', 'grpc_c')
 puts 'Generating Makefile for ' + output
 create_makefile(output)

src/ruby/ext/grpc/rb_byte_buffer.c

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_byte_buffer.h"
 
 #include <ruby/ruby.h>

src/ruby/ext/grpc/rb_call.c

@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_call.h"
 
 #include <ruby/ruby.h>

src/ruby/ext/grpc/rb_call_credentials.c

@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_call_credentials.h"
 
 #include <ruby/ruby.h>

src/ruby/ext/grpc/rb_channel.c

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_channel.h"
 
 #include <ruby/ruby.h>

src/ruby/ext/grpc/rb_channel_args.c

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_channel_args.h"
 
 #include <ruby/ruby.h>

src/ruby/ext/grpc/rb_channel_credentials.c

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_channel_credentials.h"
 
 #include <ruby/ruby.h>

src/ruby/ext/grpc/rb_completion_queue.c

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_completion_queue.h"
 
 #include <ruby/ruby.h>

src/ruby/ext/grpc/rb_event_thread.c

@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_event_thread.h"
 
 #include <stdbool.h>

src/ruby/ext/grpc/rb_grpc.c

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_grpc.h"
 
 #include <math.h>
@@ -45,6 +47,7 @@
 #include "rb_channel.h"
 #include "rb_channel_credentials.h"
 #include "rb_completion_queue.h"
+#include "rb_loader.h"
 #include "rb_server.h"
 #include "rb_server_credentials.h"
 
@@ -298,6 +301,11 @@ VALUE sym_details = Qundef;
 VALUE sym_metadata = Qundef;
 
 void Init_grpc_c() {
+  if (!grpc_rb_load_core()) {
+    rb_raise(rb_eLoadError, "Couldn't find or load gRPC's dynamic C core");
+    return;
+  }
+
   grpc_init();
 
 /* TODO: find alternative to ruby_vm_at_exit that is ok in Ruby 2.0 */

src/ruby/ext/grpc/rb_grpc_imports.generated.c

@@ -31,6 +31,7 @@
  *
  */
 
+#include <ruby/ruby.h>
 #include <grpc/support/port_platform.h>
 
 #ifdef GPR_WIN32

src/ruby/ext/grpc/rb_loader.c

@@ -0,0 +1,72 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "rb_grpc_imports.generated.h"
+
+#if GPR_WIN32
+#include <tchar.h>
+
+int grpc_rb_load_core() {
+#if GPR_ARCH_64
+  TCHAR fname[] = _T("grpc_c.64.ruby");
+#else
+  TCHAR fname[] = _T("grpc_c.32.ruby");
+#endif
+  HMODULE module = GetModuleHandle(_T("grpc_c.so"));
+  TCHAR path[2048 + 32] = _T("");
+  LPTSTR seek_back = NULL;
+  GetModuleFileName(module, path, 2048);
+
+  seek_back = _tcsrchr(path, _T('\\'));
+
+  while (seek_back) {
+    HMODULE grpc_c;
+    _tcscpy(seek_back + 1, fname);
+    grpc_c = LoadLibrary(path);
+    if (grpc_c) {
+      grpc_rb_load_imports(grpc_c);
+      return 1;
+    } else {
+      *seek_back = _T('\0');
+      seek_back = _tcsrchr(path, _T('\\'));
+    }
+  }
+
+  return 0;
+}
+
+#else
+
+int grpc_rb_load_core() { return 1; }
+
+#endif

src/ruby/ext/grpc/rb_loader.h

@@ -0,0 +1,40 @@
+/*
+ *
+ * Copyright 2016, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef GRPC_RB_LOADER_H_
+#define GRPC_RB_LOADER_H_
+
+/* Attempts to load the core if necessary, and return non-zero upon succes. */
+int grpc_rb_load_core();
+
+#endif /* GRPC_RB_BYTE_BUFFER_H_ */

src/ruby/ext/grpc/rb_server.c

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_server.h"
 
 #include <ruby/ruby.h>

src/ruby/ext/grpc/rb_server_credentials.c

@@ -1,6 +1,6 @@
 /*
  *
- * Copyright 2015, Google Inc.
+ * Copyright 2015-2016, Google Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -31,6 +31,8 @@
  *
  */
 
+#include <ruby/ruby.h>
+#include "rb_grpc_imports.generated.h"
 #include "rb_server_credentials.h"
 
 #include <ruby/ruby.h>