fix: pointer sign warnings

Author: YoussefZidan-1

input/ipc-win.c

@@ -205,7 +205,7 @@ static MP_THREAD_VOID client_thread(void *p)
     char buf[4096];
     HANDLE wakeup_event = CreateEventW(NULL, TRUE, FALSE, NULL);
     OVERLAPPED ol = { .hEvent = CreateEventW(NULL, TRUE, TRUE, NULL) };
-    bstr client_msg = { talloc_strdup(NULL, ""), 0 };
+    bstr client_msg = { (unsigned char *)talloc_strdup(NULL, ""), 0 };
     DWORD ioerr = 0;
     DWORD r;
 
@@ -269,7 +269,7 @@ static MP_THREAD_VOID client_thread(void *p)
                 goto done;
             }
 
-            bstr_xappend(NULL, &client_msg, (bstr){buf, r});
+            bstr_xappend(NULL, &client_msg, (bstr){(unsigned char *)buf, r});
             while (bstrchr(client_msg, '\n') != -1) {
                 char *reply_msg = mp_ipc_consume_next_command(arg->client,
                     NULL, &client_msg);

osdep/subprocess-win.c

@@ -65,7 +65,7 @@ static void write_arg(bstr *cmdline, char *arg)
             break;
         case '"':
             // Write the argument up to the point before the quote
-            bstr_xappend(NULL, cmdline, (struct bstr){arg, pos});
+            bstr_xappend(NULL, cmdline, (struct bstr){(unsigned char *)arg, pos});
             arg += pos;
             pos = 0;
 
@@ -107,7 +107,7 @@ static wchar_t *write_cmdline(void *ctx, char *argv0, char **args)
         }
     }
 
-    wchar_t *wcmdline = mp_from_utf8(ctx, cmdline.start);
+    wchar_t *wcmdline = mp_from_utf8(ctx, (char *)cmdline.start);
     talloc_free(cmdline.start);
     return wcmdline;
 }
@@ -382,7 +382,7 @@ void mp_subprocess2(struct mp_subprocess_opts *opts,
     // https://www.catch22.net/tuts/undocumented-createprocess>
     si.StartupInfo.cbReserved2 = sizeof(int) + crt_fd_count * (1 + sizeof(intptr_t));
     si.StartupInfo.lpReserved2 = talloc_size(tmp, si.StartupInfo.cbReserved2);
-    char *crt_buf_flags = si.StartupInfo.lpReserved2 + sizeof(int);
+    char *crt_buf_flags = (char *)si.StartupInfo.lpReserved2 + sizeof(int);
     char *crt_buf_hndls = crt_buf_flags + crt_fd_count;
 
     memcpy(si.StartupInfo.lpReserved2, &crt_fd_count, sizeof(int));