Move sys_reset_uid_gid to library

This fixes a problem where ‘gcc -fanalyzer -flto’ (GCC 10)
complained that sys_reset_uid_gid was defined but not used in some
modules.  This function belonged in a .c file anyway.
* lib/rtapelib.c (sys_reset_uid_gid):
* paxlib/rtape.c (sys_reset_uid_gid):
Move here from system.h.  The code is now duplicated, but so is
most of the rest of this file anyway.
* lib/system.h (sys_reset_uid_gid): Remove.

3 files changed, 46 insertions, 18 deletions

diff --git a/lib/rtapelib.c b/lib/rtapelib.c
index 5190cd4..1ff2eb6 100644
--- a/lib/rtapelib.c
+++ b/lib/rtapelib.c
@@ -353,6 +353,29 @@ encode_oflag (char *buf, int oflag)
   if (oflag & O_TRUNC) strcat (buf, "|O_TRUNC");
 }
 
+/* Reset user and group IDs to be those of the real user.
+   Return NULL on success, a failing syscall name (setting errno) on error.  */
+static char const *
+sys_reset_uid_gid (void)
+{
+#if !MSDOS
+  uid_t uid = getuid ();
+  gid_t gid = getgid ();
+  struct passwd *pw = getpwuid (uid);
+
+  if (!pw)
+    return "getpwuid";
+  if (initgroups (pw->pw_name, gid) != 0)
+    return "initgroups";
+  if (gid != getegid () && setgid (gid) != 0 && errno != EPERM)
+    return "setgid";
+  if (uid != geteuid () && setuid (uid) != 0 && errno != EPERM)
+    return "setuid";
+#endif
+
+  return NULL;
+}
+
 /* Open a file (a magnetic tape device?) on the system specified in
    FILE_NAME, as the given user. FILE_NAME has the form `[USER@]HOST:FILE'.
    OPEN_MODE is O_RDONLY, O_WRONLY, etc.  If successful, return the
diff --git a/lib/system.h b/lib/system.h
index 92b2462..0690363 100644
--- a/lib/system.h
+++ b/lib/system.h
@@ -465,28 +465,10 @@ char *getenv ();
 # define SET_BINARY_MODE(arc) setmode(arc, O_BINARY)
 # define mkdir(file, mode) (mkdir) (file)
 # define TTY_NAME "con"
-# define sys_reset_uid_gid()
 #else
 # define SET_BINARY_MODE(arc)
 # define TTY_NAME "/dev/tty"
 # include <paxlib.h>
-static char const *
-sys_reset_uid_gid (void)
-{
-  uid_t uid = getuid ();
-  gid_t gid = getgid ();
-  struct passwd *pw = getpwuid (uid);
-
-  if (!pw)
-    return "getpwuid";
-  if (initgroups (pw->pw_name, gid))
-    return "initgroups";
-  if (gid != getegid () && setgid (gid) && errno != EPERM)
-    return "setgid";
-  if (uid != geteuid () && setuid (uid) && errno != EPERM)
-    return "setuid";
-  return NULL;
-}
 #endif
 
 #if XENIX
diff --git a/paxlib/rtape.c b/paxlib/rtape.c
index 2364594..1089d92 100644
--- a/paxlib/rtape.c
+++ b/paxlib/rtape.c
@@ -358,6 +358,29 @@ encode_oflag (char *buf, int oflag)
     strcat (buf, "|O_TRUNC");
 }
 
+/* Reset user and group IDs to be those of the real user.
+   Return NULL on success, a failing syscall name (setting errno) on error.  */
+static char const *
+sys_reset_uid_gid (void)
+{
+#if !MSDOS
+  uid_t uid = getuid ();
+  gid_t gid = getgid ();
+  struct passwd *pw = getpwuid (uid);
+
+  if (!pw)
+    return "getpwuid";
+  if (initgroups (pw->pw_name, gid) != 0)
+    return "initgroups";
+  if (gid != getegid () && setgid (gid) != 0 && errno != EPERM)
+    return "setgid";
+  if (uid != geteuid () && setuid (uid) != 0 && errno != EPERM)
+    return "setuid";
+#endif
+
+  return NULL;
+}
+
 /* Open a remote file on the system specified in FILE_NAME, as the given user.
    FILE_NAME has the form `[USER@]HOST:FILE'.
    OPEN_MODE is O_RDONLY, O_WRONLY, etc.  If successful, return the