os-posix: Clean up global variable shadowing

Fix:

  os-posix.c:103:31: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
  bool os_set_runas(const char *optarg)
                                ^
  os-posix.c:176:32: error: declaration shadows a variable in the global scope [-Werror,-Wshadow]
  void os_set_chroot(const char *optarg)
                                 ^
  /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/getopt.h:77:14: note: previous declaration is here
  extern char *optarg;                    /* getopt(3) external variables */
               ^

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231004120019.93101-5-philmd@linaro.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

include/sysemu/os-posix.h

@@ -49,8 +49,8 @@ void os_setup_signal_handling(void);
 int os_set_daemonize(bool d);
 bool is_daemonized(void);
 void os_daemonize(void);
-bool os_set_runas(const char *optarg);
-void os_set_chroot(const char *optarg);
+bool os_set_runas(const char *user_id);
+void os_set_chroot(const char *path);
 void os_setup_post(void);
 int os_mlock(void);
 

os-posix.c

@@ -94,13 +94,13 @@ static uid_t user_uid = (uid_t)-1; /*   -1      -1        >=0    */
 static gid_t user_gid = (gid_t)-1; /*   -1      -1        >=0    */
 
 /*
- * Prepare to change user ID. optarg can be one of 3 forms:
+ * Prepare to change user ID. user_id can be one of 3 forms:
  *   - a username, in which case user ID will be changed to its uid,
  *     with primary and supplementary groups set up too;
  *   - a numeric uid, in which case only the uid will be set;
  *   - a pair of numeric uid:gid.
  */
-bool os_set_runas(const char *optarg)
+bool os_set_runas(const char *user_id)
 {
     unsigned long lv;
     const char *ep;
@@ -108,14 +108,14 @@ bool os_set_runas(const char *optarg)
     gid_t got_gid;
     int rc;
 
-    user_pwd = getpwnam(optarg);
+    user_pwd = getpwnam(user_id);
     if (user_pwd) {
         user_uid = -1;
         user_gid = -1;
         return true;
     }
 
-    rc = qemu_strtoul(optarg, &ep, 0, &lv);
+    rc = qemu_strtoul(user_id, &ep, 0, &lv);
     got_uid = lv; /* overflow here is ID in C99 */
     if (rc || *ep != ':' || got_uid != lv || got_uid == (uid_t)-1) {
         return false;
@@ -173,9 +173,9 @@ static void change_process_uid(void)
 
 static const char *chroot_dir;
 
-void os_set_chroot(const char *optarg)
+void os_set_chroot(const char *path)
 {
-    chroot_dir = optarg;
+    chroot_dir = path;
 }
 
 static void change_root(void)