Add a convenience macro for the returns_twice attribute, and apply it to

the prototypes of the appropriate functions (getcontext, savectx,
setjmp, sigsetjmp and vfork).

MFC after:	2 weeks

12 files changed, 20 insertions, 14 deletions

diff --git a/include/setjmp.h b/include/setjmp.h
index 49d4ed5..bf03f6f 100644
--- a/include/setjmp.h
+++ b/include/setjmp.h
@@ -46,16 +46,16 @@
 __BEGIN_DECLS
 #if __BSD_VISIBLE || __XSI_VISIBLE >= 600
 void	_longjmp(jmp_buf, int) __dead2;
-int	_setjmp(jmp_buf);
+int	_setjmp(jmp_buf) __returns_twice;
 #endif
 void	longjmp(jmp_buf, int) __dead2;
 #if __BSD_VISIBLE
 void	longjmperror(void);
 #endif
-int	setjmp(jmp_buf);
+int	setjmp(jmp_buf) __returns_twice;
 #if __BSD_VISIBLE || __POSIX_VISIBLE || __XSI_VISIBLE
 void	siglongjmp(sigjmp_buf, int) __dead2;
-int	sigsetjmp(sigjmp_buf, int);
+int	sigsetjmp(sigjmp_buf, int) __returns_twice;
 #endif
 __END_DECLS
 
diff --git a/include/unistd.h b/include/unistd.h
index 90694ed..9b2f2ec 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -479,7 +479,7 @@ char	*getwd(char *);			/* obsoleted by getcwd() */
 useconds_t
 	 ualarm(useconds_t, useconds_t);
 int	 usleep(useconds_t);
-pid_t	 vfork(void);
+pid_t	 vfork(void) __returns_twice;
 #endif
 
 #if __BSD_VISIBLE
diff --git a/sys/amd64/include/pcb.h b/sys/amd64/include/pcb.h
index 61f651bb..70b2e62 100644
--- a/sys/amd64/include/pcb.h
+++ b/sys/amd64/include/pcb.h
@@ -130,7 +130,7 @@ clear_pcb_flags(struct pcb *pcb, const u_int flags)
 }
 
 void	makectx(struct trapframe *, struct pcb *);
-int	savectx(struct pcb *);
+int	savectx(struct pcb *) __returns_twice;
 
 #endif
 
diff --git a/sys/arm/include/pcb.h b/sys/arm/include/pcb.h
index 4a5f330..ce9ab97 100644
--- a/sys/arm/include/pcb.h
+++ b/sys/arm/include/pcb.h
@@ -94,7 +94,7 @@ void	makectx(struct trapframe *tf, struct pcb *pcb);
 
 #ifdef _KERNEL
 
-void    savectx(struct pcb *);
+void    savectx(struct pcb *) __returns_twice;
 #endif	/* _KERNEL */
 
 #endif	/* !_MACHINE_PCB_H_ */
diff --git a/sys/i386/include/pcb.h b/sys/i386/include/pcb.h
index 1311ab1..4c227df 100644
--- a/sys/i386/include/pcb.h
+++ b/sys/i386/include/pcb.h
@@ -84,7 +84,7 @@ struct pcb {
 struct trapframe;
 
 void	makectx(struct trapframe *, struct pcb *);
-void	savectx(struct pcb *);
+void	savectx(struct pcb *) __returns_twice;
 #endif
 
 #endif /* _I386_PCB_H_ */
diff --git a/sys/ia64/include/pcb.h b/sys/ia64/include/pcb.h
index 59334bf..dac7169 100644
--- a/sys/ia64/include/pcb.h
+++ b/sys/ia64/include/pcb.h
@@ -65,10 +65,10 @@ struct trapframe;
 
 void makectx(struct trapframe *, struct pcb *);
 void restorectx(struct pcb *) __dead2;
-int swapctx(struct pcb *old, struct pcb *new);
+int swapctx(struct pcb *old, struct pcb *new) __returns_twice;
 
 void ia32_restorectx(struct pcb *);
-void ia32_savectx(struct pcb *);
+void ia32_savectx(struct pcb *) __returns_twice;
 
 #endif
 
diff --git a/sys/mips/include/pcb.h b/sys/mips/include/pcb.h
index 9911339..52589f5 100644
--- a/sys/mips/include/pcb.h
+++ b/sys/mips/include/pcb.h
@@ -78,7 +78,7 @@ struct pcb
 extern struct pcb *curpcb;		/* the current running pcb */
 
 void makectx(struct trapframe *, struct pcb *);
-int savectx(struct pcb *);
+int savectx(struct pcb *) __returns_twice;
 #endif
 
 #endif	/* !_MACHINE_PCB_H_ */
diff --git a/sys/powerpc/include/cpu.h b/sys/powerpc/include/cpu.h
index 73b1f50..66d21eb 100644
--- a/sys/powerpc/include/cpu.h
+++ b/sys/powerpc/include/cpu.h
@@ -99,6 +99,6 @@ void	fork_trampoline(void);
 void	swi_vm(void *);
 
 /* XXX the following should not be here. */
-void	savectx(struct pcb *);
+void	savectx(struct pcb *) __returns_twice;
 
 #endif	/* _MACHINE_CPU_H_ */
diff --git a/sys/sparc64/include/pcb.h b/sys/sparc64/include/pcb.h
index f23c1f2..25a41cc 100644
--- a/sys/sparc64/include/pcb.h
+++ b/sys/sparc64/include/pcb.h
@@ -55,7 +55,7 @@ struct pcb {
 
 #ifdef _KERNEL
 void	makectx(struct trapframe *tf, struct pcb *pcb);
-int	savectx(struct pcb *pcb);
+int	savectx(struct pcb *pcb) __returns_twice;
 #endif
 
 #endif /* !LOCORE */
diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
index 076842d..80f7b8e 100644
--- a/sys/sys/cdefs.h
+++ b/sys/sys/cdefs.h
@@ -293,6 +293,12 @@
 #define __nonnull(x)
 #endif
 
+#if __GNUC_PREREQ__(4, 1)
+#define	__returns_twice	__attribute__((__returns_twice__))
+#else
+#define	__returns_twice
+#endif
+
 /* XXX: should use `#if __STDC_VERSION__ < 199901'. */
 #if !__GNUC_PREREQ__(2, 7) && !defined(__INTEL_COMPILER)
 #define	__func__	NULL
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
index 5375ec4..fec77d2 100644
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -153,7 +153,7 @@ struct uio;
 struct _jmp_buf;
 struct trapframe;
 
-int	setjmp(struct _jmp_buf *);
+int	setjmp(struct _jmp_buf *) __returns_twice;
 void	longjmp(struct _jmp_buf *, int) __dead2;
 int	dumpstatus(vm_offset_t addr, off_t count);
 int	nullop(void);
diff --git a/sys/sys/ucontext.h b/sys/sys/ucontext.h
index 609cdd3..1e504c9 100644
--- a/sys/sys/ucontext.h
+++ b/sys/sys/ucontext.h
@@ -71,7 +71,7 @@ struct ucontext4 {
 
 __BEGIN_DECLS
 
-int	getcontext(ucontext_t *);
+int	getcontext(ucontext_t *) __returns_twice;
 ucontext_t *getcontextx(void);
 int	setcontext(const ucontext_t *);
 void	makecontext(ucontext_t *, void (*)(void), int, ...);