Some windows build errors

src/core/lib/support/log_windows.cc

@@ -47,7 +47,7 @@ void gpr_log(const char *file, int line, gpr_log_severity severity,
   } else {
     /* Allocate a new buffer, with space for the NUL terminator. */
     size_t strp_buflen = (size_t)ret + 1;
-    message = gpr_malloc(strp_buflen);
+    message = (char *)gpr_malloc(strp_buflen);
 
     /* Print to the buffer. */
     va_start(args, format);
@@ -66,7 +66,7 @@ void gpr_log(const char *file, int line, gpr_log_severity severity,
 
 /* Simple starter implementation */
 extern "C" void gpr_default_log(gpr_log_func_args *args) {
-  char *final_slash;
+  const char *final_slash;
   const char *display_file;
   char time_buffer[64];
   time_t timer;

src/core/lib/support/string_windows.cc

@@ -47,7 +47,7 @@ int gpr_asprintf(char **strp, const char *format, ...) {
 
   /* Allocate a new buffer, with space for the NUL terminator. */
   strp_buflen = (size_t)ret + 1;
-  if ((*strp = gpr_malloc(strp_buflen)) == NULL) {
+  if ((*strp = (char *)gpr_malloc(strp_buflen)) == NULL) {
     /* This shouldn't happen, because gpr_malloc() calls abort(). */
     return -1;
   }

src/core/lib/support/subprocess_windows.cc

@@ -61,7 +61,7 @@ gpr_subprocess *gpr_subprocess_create(int argc, const char **argv) {
   }
   gpr_free(args_tchar);
 
-  r = gpr_malloc(sizeof(gpr_subprocess));
+  r = (gpr_subprocess *)gpr_malloc(sizeof(gpr_subprocess));
   memset(r, 0, sizeof(*r));
   r->pi = pi;
   return r;

src/core/lib/support/sync_windows.cc

@@ -104,7 +104,7 @@ struct run_once_func_arg {
   void (*init_function)(void);
 };
 static BOOL CALLBACK run_once_func(gpr_once *once, void *v, void **pv) {
-  struct run_once_func_arg *arg = v;
+  struct run_once_func_arg *arg = (struct run_once_func_arg *)v;
   (*arg->init_function)();
   return 1;
 }