More fixes.

src/core/iomgr/iocp_windows.c

@@ -67,7 +67,7 @@ static DWORD deadline_to_millis_timeout(gpr_timespec deadline,
     return 0;
   }
   timeout = gpr_time_sub(deadline, now);
-  return gpr_time_to_millis(gpr_time_add(
+  return (DWORD)gpr_time_to_millis(gpr_time_add(
       timeout, gpr_time_from_nanos(GPR_NS_PER_MS - 1, GPR_TIMESPAN)));
 }
 
@@ -179,11 +179,9 @@ void grpc_iocp_add_socket(grpc_winsocket *socket) {
 static void socket_notify_on_iocp(grpc_exec_ctx *exec_ctx,
                                   grpc_winsocket *socket, grpc_closure *closure,
                                   grpc_winsocket_callback_info *info) {
-  int run_now = 0;
   GPR_ASSERT(info->closure == NULL);
   gpr_mu_lock(&socket->state_mu);
   if (info->has_pending_iocp) {
-    run_now = 1;
     info->has_pending_iocp = 0;
     grpc_exec_ctx_enqueue(exec_ctx, closure, 1);
   } else {

src/core/iomgr/tcp_windows.c

@@ -143,10 +143,7 @@ static void on_read(grpc_exec_ctx *exec_ctx, void *tcpp, int success) {
   grpc_closure *cb = tcp->read_cb;
   grpc_winsocket *socket = tcp->socket;
   gpr_slice sub;
-  gpr_slice *slice = NULL;
-  size_t nslices = 0;
   grpc_winsocket_callback_info *info = &socket->read_info;
-  int do_abort = 0;
 
   if (success) {
     if (socket->read_info.wsa_error != 0 && !tcp->shutting_down) {
@@ -238,7 +235,6 @@ static void on_write(grpc_exec_ctx *exec_ctx, void *tcpp, int success) {
   grpc_winsocket *handle = tcp->socket;
   grpc_winsocket_callback_info *info = &handle->write_info;
   grpc_closure *cb;
-  int do_abort = 0;
 
   gpr_mu_lock(&tcp->mu);
   cb = tcp->write_cb;

src/core/support/env_win32.c

@@ -38,7 +38,12 @@
 #include "src/core/support/env.h"
 #include "src/core/support/string.h"
 
+#ifdef __MINGW32__
+errno_t getenv_s(size_t *size_needed, char *buffer, size_t size,
+                 const char *varname);
+#else
 #include <stdlib.h>
+#endif
 
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>