libthr: fix warnings from GCC when WARNS=6

Fix warnings about:
- redundant declarations
- a local variable shadowing a global function (dlinfo)
- an old-style function definition (with an empty parameter list)
- a variable that is possibly used uninitialized

"make tinderbox" passes this time, except for a few unrelated
kernel failures.

Reviewed by:	kib
MFC after:	3 days
Sponsored by:	Dell EMC
Differential Revision:	https://reviews.freebsd.org/D10870

include/stdio.h

@@ -464,7 +464,10 @@ static __inline int __sputc(int _c, FILE *_p) {
 		(*(p)->_p = (c), (int)*(p)->_p++))
 #endif
 
+#ifndef __LIBC_ISTHREADED_DECLARED
+#define __LIBC_ISTHREADED_DECLARED
 extern int __isthreaded;
+#endif
 
 #ifndef __cplusplus
 

lib/libc/include/libc_private.h

@@ -42,7 +42,10 @@
  * or more threads. It is used to avoid calling locking functions
  * when they are not required.
  */
+#ifndef __LIBC_ISTHREADED_DECLARED
+#define __LIBC_ISTHREADED_DECLARED
 extern int	__isthreaded;
+#endif
 
 /*
  * Elf_Auxinfo *__elf_aux_vector, the pointer to the ELF aux vector

lib/libthr/thread/thr_exit.c

@@ -46,8 +46,6 @@ __FBSDID("$FreeBSD$");
 #include "libc_private.h"
 #include "thr_private.h"
 
-void	_pthread_exit(void *status);
-
 static void	exit_thread(void) __dead2;
 
 __weak_reference(_pthread_exit, pthread_exit);
@@ -72,7 +70,7 @@ static void
 thread_uw_init(void)
 {
 	static int inited = 0;
-	Dl_info dlinfo;
+	Dl_info dli;
 	void *handle;
 	void *forcedunwind, *getcfa;
 
@@ -80,12 +78,12 @@ thread_uw_init(void)
 	    return;
 	handle = RTLD_DEFAULT;
 	if ((forcedunwind = dlsym(handle, "_Unwind_ForcedUnwind")) != NULL) {
-	    if (dladdr(forcedunwind, &dlinfo)) {
+	    if (dladdr(forcedunwind, &dli)) {
 		/*
 		 * Make sure the address is always valid by holding the library,
 		 * also assume functions are in same library.
 		 */
-		if ((handle = dlopen(dlinfo.dli_fname, RTLD_LAZY)) != NULL) {
+		if ((handle = dlopen(dli.dli_fname, RTLD_LAZY)) != NULL) {
 		    forcedunwind = dlsym(handle, "_Unwind_ForcedUnwind");
 		    getcfa = dlsym(handle, "_Unwind_GetCFA");
 		    if (forcedunwind != NULL && getcfa != NULL) {

lib/libthr/thread/thr_kern.c

@@ -62,7 +62,7 @@ _thr_setthreaded(int threaded)
 }
 
 void
-_thr_assert_lock_level()
+_thr_assert_lock_level(void)
 {
 	PANIC("locklevel <= 0");
 }

lib/libthr/thread/thr_list.c

@@ -35,8 +35,8 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 #include <pthread.h>
 
-#include "thr_private.h"
 #include "libc_private.h"
+#include "thr_private.h"
 
 /*#define DEBUG_THREAD_LIST */
 #ifdef DEBUG_THREAD_LIST

lib/libthr/thread/thr_mutex.c

@@ -70,8 +70,6 @@ int	__pthread_mutex_trylock(pthread_mutex_t *mutex);
 int	__pthread_mutex_lock(pthread_mutex_t *mutex);
 int	__pthread_mutex_timedlock(pthread_mutex_t *mutex,
 		const struct timespec *abstime);
-int	_pthread_mutex_init_calloc_cb(pthread_mutex_t *mutex,
-    		void *(calloc_cb)(size_t, size_t));
 int	_pthread_mutex_getspinloops_np(pthread_mutex_t *mutex, int *count);
 int	_pthread_mutex_setspinloops_np(pthread_mutex_t *mutex, int count);
 int	__pthread_mutex_setspinloops_np(pthread_mutex_t *mutex, int count);
@@ -712,6 +710,7 @@ mutex_lock_common(struct pthread_mutex *m, const struct timespec *abstime,
 	struct pthread *curthread;
 	int ret, robust;
 
+	robust = 0;  /* pacify gcc */
 	curthread  = _get_curthread();
 	if (!cvattach && m->m_flags & PMUTEX_FLAG_PRIVATE)
 		THR_CRITICAL_ENTER(curthread);

lib/libthr/thread/thr_private.h

@@ -701,7 +701,10 @@ do {								\
 	(curthr->report_events && 			\
 	 (((curthr)->event_mask | _thread_event_mask ) & e) != 0)
 
+#ifndef __LIBC_ISTHREADED_DECLARED
+#define __LIBC_ISTHREADED_DECLARED
 extern int __isthreaded;
+#endif
 
 /*
  * Global variables for the pthread kernel.
@@ -835,8 +838,10 @@ int	_sched_yield(void);
 void	_pthread_cleanup_push(void (*)(void *), void *);
 void	_pthread_cleanup_pop(int);
 void	_pthread_exit_mask(void *status, sigset_t *mask) __dead2 __hidden;
+#ifndef _LIBC_PRIVATE_H_
 void	_pthread_cancel_enter(int maycancel);
 void 	_pthread_cancel_leave(int maycancel);
+#endif
 int	_pthread_mutex_consistent(pthread_mutex_t * _Nonnull);
 int	_pthread_mutexattr_getrobust(pthread_mutexattr_t * _Nonnull __restrict,
 	    int * _Nonnull __restrict);
@@ -844,46 +849,56 @@ int	_pthread_mutexattr_setrobust(pthread_mutexattr_t * _Nonnull, int);
 
 /* #include <fcntl.h> */
 #ifdef  _SYS_FCNTL_H_
+#ifndef _LIBC_PRIVATE_H_
 int     __sys_fcntl(int, int, ...);
 int     __sys_openat(int, const char *, int, ...);
-#endif
+#endif /* _LIBC_PRIVATE_H_ */
+#endif /* _SYS_FCNTL_H_ */
 
 /* #include <signal.h> */
 #ifdef _SIGNAL_H_
 int	__sys_kill(pid_t, int);
-int     __sys_sigaction(int, const struct sigaction *, struct sigaction *);
+int     __sys_sigaltstack(const struct sigaltstack *, struct sigaltstack *);
 int     __sys_sigpending(sigset_t *);
+int     __sys_sigreturn(const ucontext_t *);
+#ifndef _LIBC_PRIVATE_H_
+int     __sys_sigaction(int, const struct sigaction *, struct sigaction *);
 int     __sys_sigprocmask(int, const sigset_t *, sigset_t *);
 int     __sys_sigsuspend(const sigset_t *);
-int     __sys_sigreturn(const ucontext_t *);
-int     __sys_sigaltstack(const struct sigaltstack *, struct sigaltstack *);
-int	__sys_sigwait(const sigset_t *, int *);
 int	__sys_sigtimedwait(const sigset_t *, siginfo_t *,
 		const struct timespec *);
+int	__sys_sigwait(const sigset_t *, int *);
 int	__sys_sigwaitinfo(const sigset_t *set, siginfo_t *info);
-#endif
+#endif /* _LIBC_PRIVATE_H_ */
+#endif /* _SYS_FCNTL_H_ */
 
 /* #include <time.h> */
 #ifdef	_TIME_H_
+#ifndef _LIBC_PRIVATE_H_
 int	__sys_clock_nanosleep(clockid_t, int, const struct timespec *,
 	    struct timespec *);
 int	__sys_nanosleep(const struct timespec *, struct timespec *);
-#endif
+#endif /* _LIBC_PRIVATE_H_ */
+#endif /* _SYS_FCNTL_H_ */
 
 /* #include <sys/ucontext.h> */
 #ifdef _SYS_UCONTEXT_H_
+#ifndef _LIBC_PRIVATE_H_
 int	__sys_setcontext(const ucontext_t *ucp);
 int	__sys_swapcontext(ucontext_t *oucp, const ucontext_t *ucp);
-#endif
+#endif /* _LIBC_PRIVATE_H_ */
+#endif /* _SYS_FCNTL_H_ */
 
 /* #include <unistd.h> */
 #ifdef  _UNISTD_H_
+void	__sys_exit(int);
+pid_t	__sys_getpid(void);
+#ifndef _LIBC_PRIVATE_H_
 int     __sys_close(int);
 int	__sys_fork(void);
-pid_t	__sys_getpid(void);
 ssize_t __sys_read(int, void *, size_t);
-void	__sys_exit(int);
-#endif
+#endif /* _LIBC_PRIVATE_H_ */
+#endif /* _SYS_FCNTL_H_ */
 
 static inline int
 _thr_isthreaded(void)