Introduce usage of __builtin_unreachable() and noreturn (#248)

This commit adds an UNREACHABLE() macro that expands to either the
__builtin_unreachable() compiler builtin (for release builds) or
abort(3) (for development builds). This is used to mark code paths
that are never to be reached.

It also adds the 'noreturn' attribute to functions that never
return: path_exec(), sh_done() and sh_syntax(). The UNREACHABLE()
macro is not added after calling these.

The purpose of these is:
* to slightly improve GCC/Clang compiler optimizations;
* to fix a few compiler warnings;
* to add code clarity.

Changes of note:

src/cmd/ksh93/sh/io.c: outexcept():
- Avoid using __builtin_unreachable() here since errormsg can
  return despite using ERROR_system(1), as shp->jmplist->mode is
  temporarily set to 0. See: https://github.com/att/ast/issues/1336

src/cmd/ksh93/tests/io.sh:
- Add a regression test for the ksh2020 bug referenced above.

src/lib/libast/features/common:
- Detect the existence of either the C11 stdnoreturn.h header or
  the GCC noreturn attribute, preferring the former when available.
- Test for the existence of __builtin_unreachable(). Use it for
  release builds. On development builds, use abort() instead, which
  crahses reliably for debugging when unreachable code is reached.

Co-authored-by: Martijn Dekker <martijn@inlv.org>

src/cmd/ksh93/bltins/alarm.c

@@ -256,19 +256,25 @@ int	b_alarm(int argc,char *argv[],Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	argc -= opt_info.index;
 	argv += opt_info.index;
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(argc==0)
 	{
 		print_alarms(shp->st.timetrap);
 		return(0);
 	}
 	if(argc!=2)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),optusage((char*)0));
+		UNREACHABLE();
+	}
 	np = nv_open(argv[0],shp->var_tree,NV_NOARRAY|NV_VARNAME|NV_NOASSIGN);
 	if(!nv_isnull(np))
 		nv_unset(np);

src/cmd/ksh93/bltins/cd_pwd.c

@@ -60,7 +60,10 @@ int	b_cd(int argc, char *argv[],Shbltin_t *context)
 	static char *oldpwd;
 	Namval_t *opwdnod, *pwdnod;
 	if(sh_isoption(SH_RESTRICTED))
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_restricted+4);
+		UNREACHABLE();
+	}
 	while((rval = optget(argv,sh_optcd))) switch(rval)
 	{
 		case 'L':
@@ -74,13 +77,16 @@ int	b_cd(int argc, char *argv[],Shbltin_t *context)
 			break;
 		case '?':
 			errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-			break;
+			UNREACHABLE();
 	}
 	argv += opt_info.index;
 	argc -= opt_info.index;
 	dir =  argv[0];
 	if(error_info.errors>0 || argc >2)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(oldpwd && oldpwd!=shp->pwd && oldpwd!=e_dot)
 		free(oldpwd);
 	oldpwd = path_pwd(shp,0);
@@ -98,7 +104,10 @@ int	b_cd(int argc, char *argv[],Shbltin_t *context)
 	else if(*dir == '-' && dir[1]==0)
 		dir = nv_getval(opwdnod);
 	if(!dir || *dir==0)
+	{
 		errormsg(SH_DICT,ERROR_exit(1),argc==2?e_subst+4:e_direct);
+		UNREACHABLE();
+	}
 	/*
 	 * If sh_subshell() in subshell.c cannot use fchdir(2) to restore the PWD using a saved file descriptor,
 	 * we must fork any virtual subshell now to avoid the possibility of ending up in the wrong PWD on exit.
@@ -193,6 +202,7 @@ int	b_cd(int argc, char *argv[],Shbltin_t *context)
 		if(saverrno)
 			errno = saverrno;
 		errormsg(SH_DICT,ERROR_system(1),"%s:",dir);
+		UNREACHABLE();
 	}
 success:
 	if(dir == nv_getval(opwdnod) || argc==2)
@@ -204,6 +214,7 @@ success:
 		{
 			dir = stakptr(PATH_OFFSET);
 			errormsg(SH_DICT,ERROR_system(1),"%s:",dir);
+			UNREACHABLE();
 		}
 		stakseek(dir-stakptr(0));
 	}
@@ -245,12 +256,18 @@ int	b_pwd(int argc, char *argv[],Shbltin_t *context)
 			break;
 		case '?':
 			errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-			break;
+			UNREACHABLE();
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(*(cp = path_pwd(shp,0)) != '/')
+	{
 		errormsg(SH_DICT,ERROR_system(1), e_pwd);
+		UNREACHABLE();
+	}
 	if(flag)
 	{
 		cp = strcpy(stakseek(strlen(cp)+PATH_MAX),cp);

src/cmd/ksh93/bltins/cflow.c

@@ -61,7 +61,10 @@ int	b_return(register int n, register char *argv[],Shbltin_t *context)
 	}
 done:
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	pp->mode = (**argv=='e'?SH_JMPEXIT:SH_JMPFUN);
 	argv += opt_info.index;
 	n = (arg = *argv) ? (int)strtol(arg, (char**)0, 10) : shp->savexit;
@@ -98,14 +101,20 @@ int	b_break(register int n, register char *argv[],Shbltin_t *context)
 		return(2);
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 	n=1;
 	if(arg= *argv)
 	{
 		n = (int)strtol(arg,&arg,10);
 		if(n<=0 || *arg)
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_nolabels,*argv);
+			UNREACHABLE();
+		}
 	}
 	if(shp->st.loopcnt)
 	{

src/cmd/ksh93/bltins/enum.c

@@ -150,6 +150,7 @@ static void put_enum(Namval_t* np,const char *val,int flags,Namfun_t *fp)
 		i++;
 	}
 	error(ERROR_exit(1), "%s: invalid value %s",nv_name(np),val);
+	UNREACHABLE();
 }
 
 static char* get_enum(register Namval_t* np, Namfun_t *fp)
@@ -196,8 +197,8 @@ int b_enum(int argc, char** argv, Shbltin_t *context)
 			iflag = 'i';
 			continue;
 		case '?':
-			error(ERROR_USAGE|4, "%s", opt_info.arg);
-			break;
+			error(ERROR_usage(2), "%s", opt_info.arg);
+			UNREACHABLE();
 		case ':':
 			error(2, "%s", opt_info.arg);
 			break;
@@ -213,7 +214,10 @@ int b_enum(int argc, char** argv, Shbltin_t *context)
 	while(cp = *argv++)
 	{
 		if(!(np = nv_open(cp, (void*)0, NV_VARNAME|NV_NOADD))  || !(ap=nv_arrayptr(np)) || ap->fun || (sz=ap->nelem&(((1L<<ARRAY_BITS)-1))) < 2)
-			error(ERROR_exit(1), "%s must name an array  containing at least two elements",cp);
+		{
+			error(ERROR_exit(1), "%s must name an array containing at least two elements",cp);
+			UNREACHABLE();
+		}
 		n = staktell();
 		sfprintf(stkstd,"%s.%s%c",NV_CLASS,np->nvname,0);
 		tp = nv_open(stakptr(n), shp->var_tree, NV_VARNAME);

src/cmd/ksh93/bltins/getopts.c

@@ -84,12 +84,15 @@ int	b_getopts(int argc,char *argv[],Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	argv += opt_info.index;
 	argc -= opt_info.index;
 	if(error_info.errors || argc<2)
+	{
 		errormsg(SH_DICT,ERROR_usage(2), "%s", optusage((char*)0));
+		UNREACHABLE();
+	}
 	error_info.context->flags |= ERROR_SILENT;
 	error_info.id = options;
 	options = argv[0];
@@ -126,7 +129,10 @@ int	b_getopts(int argc,char *argv[],Shbltin_t *context)
 	{
 	    case '?':
 		if(mode==0)
+		{
 			errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
+			UNREACHABLE();
+		}
 		opt_info.option[1] = '?';
 		/* FALLTHROUGH */
 	    case ':':
@@ -160,7 +166,10 @@ int	b_getopts(int argc,char *argv[],Shbltin_t *context)
 			optget(com,options);
 			opt_info.index = flag;
 			if(!mode && strchr(options,' '))
+			{
 				errormsg(SH_DICT,ERROR_usage(2), "%s", optusage((char*)0));
+				UNREACHABLE();
+			}
 		}
 		opt_info.arg = 0;
 		options = value;

src/cmd/ksh93/bltins/hist.c

@@ -57,7 +57,10 @@ int	b_hist(int argc,char *argv[], Shbltin_t *context)
 	Histloc_t location;
 	NOT_USED(argc);
 	if(!sh_histinit((void*)shp))
+	{
 		errormsg(SH_DICT,ERROR_system(1),e_histopen);
+		UNREACHABLE();
+	}
 	hp = shp->gd->hist_ptr;
 	while((flag = optget(argv,sh_opthist))) switch(flag)
 	{
@@ -95,10 +98,13 @@ int	b_hist(int argc,char *argv[], Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	argv += (opt_info.index-1);
 #if SHOPT_HISTEXPAND
 	if(pflag)
@@ -147,7 +153,10 @@ int	b_hist(int argc,char *argv[], Shbltin_t *context)
 		/* search for last line starting with string */
 		location = hist_find(hp,argv[1],hist_max(hp)-1,0,-1);
 		if((range[++flag] = location.hist_command) < 0)
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_found,argv[1]);
+			UNREACHABLE();
+		}
 		argv++;
 	}
 	if(flag <0)
@@ -174,9 +183,15 @@ int	b_hist(int argc,char *argv[], Shbltin_t *context)
 		range[1] = flag;
 	/* check for valid ranges */
 	if(range[1]<index2 || range[0]>=flag)
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_badrange,range[0],range[1]);
+		UNREACHABLE();
+	}
 	if(edit && *edit=='-' && range[0]!=range[1])
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_eneedsarg);
+		UNREACHABLE();
+	}
 	/* now list commands from range[flag] to range[1-flag] */
 	incr = 1;
 	flag = rflag>0;
@@ -190,9 +205,15 @@ int	b_hist(int argc,char *argv[], Shbltin_t *context)
 	else
 	{
 		if(!(fname=pathtmp(NIL(char*),0,0,NIL(int*))))
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_create,"");
+			UNREACHABLE();
+		}
 		if((fdo=open(fname,O_CREAT|O_RDWR,S_IRUSR|S_IWUSR)) < 0)
+		{
 			errormsg(SH_DICT,ERROR_system(1),e_create,fname);
+			UNREACHABLE();
+		}
 		outfile= sfnew(NIL(Sfio_t*),shp->outbuff,IOBSIZE,fdo,SF_WRITE);
 		arg = "\n";
 		nflag++;
@@ -219,7 +240,10 @@ int	b_hist(int argc,char *argv[], Shbltin_t *context)
 	{
 		arg = (char*)e_defedit;
 		if(*arg!='/')
+		{
 			errormsg(SH_DICT,ERROR_exit(1),"ed not found set FCEDIT");
+			UNREACHABLE();
+		}
 	}
 	if(*arg != '-')
 	{
@@ -246,7 +270,10 @@ int	b_hist(int argc,char *argv[], Shbltin_t *context)
 		Sfio_t *iop = sfnew(NIL(Sfio_t*),buff,IOBSIZE,fdo,SF_READ);
 		/* read in and run the command */
 		if(shp->hist_depth++ > HIST_RECURSE)
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_toodeep,"history");
+			UNREACHABLE();
+		}
 		sh_eval(iop,1);
 		shp->hist_depth--;
 	}
@@ -284,7 +311,10 @@ static void hist_subst(const char *command,int fd,char *replace)
 	string[c] = 0;
 	*newp++ =  0;
 	if((sp=sh_substitute(string,replace,newp))==0)
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_subst,command);
+		UNREACHABLE();
+	}
 	*(newp-1) =  '=';
 	sh_eval(sfopen(NIL(Sfio_t*),sp,"s"),1);
 }

src/cmd/ksh93/bltins/misc.c

@@ -113,18 +113,27 @@ int    b_exec(int argc,char *argv[], Shbltin_t *context)
 		return(2);
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(*argv[0]=='r' && argv[opt_info.index])  /* 'redirect' supports no args */
+	{
 		errormsg(SH_DICT,ERROR_exit(2),"%s: %s",e_badsyntax,argv[opt_info.index]);
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 	if(!*argv)
 		return(0);
 
 	/* from here on, it's 'exec' with args, so we're replacing the shell */
 	if(sh_isoption(SH_RESTRICTED))
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_restricted,argv[0]);
+		UNREACHABLE();
+	}
 	else
-        {
+	{
 		register struct argnod *arg=logdata.sh->envlist;
 		register Namval_t* np;
 		register char *cp;
@@ -157,7 +166,6 @@ int    b_exec(int argc,char *argv[], Shbltin_t *context)
 		sh_sigreset(2);
 		sh_freeup(logdata.sh);
 		path_exec(logdata.sh,pname,argv,NIL(struct argnod*));
-		sh_done(logdata.sh,0);
         }
 	return(1);
 }
@@ -175,11 +183,14 @@ int    b_let(int argc,char *argv[],Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	argv += opt_info.index;
 	if(error_info.errors || !*argv)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	while(arg= *argv++)
 		r = !sh_arith(shp,arg);
 	return(r);
@@ -200,7 +211,10 @@ int    b_eval(int argc,char *argv[], Shbltin_t *context)
 		return(2);
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 	if(*argv && **argv)
 	{
@@ -236,9 +250,15 @@ int    b_dot_cmd(register int n,char *argv[],Shbltin_t *context)
 	argv += opt_info.index;
 	script = *argv;
 	if(error_info.errors || !script)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(shp->dot_depth+1 > DOTMAX)
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_toodeep,script);
+		UNREACHABLE();
+	}
 	if(!(np=shp->posix_fun))
 	{
 		/* check for KornShell style function first */
@@ -254,7 +274,10 @@ int    b_dot_cmd(register int n,char *argv[],Shbltin_t *context)
 						np = 0;
 				}
 				else
+				{
 					errormsg(SH_DICT,ERROR_exit(1),e_found,script);
+					UNREACHABLE();
+				}
 			}
 		}
 		else
@@ -262,7 +285,10 @@ int    b_dot_cmd(register int n,char *argv[],Shbltin_t *context)
 		if(!np)
 		{
 			if((fd=path_open(shp,script,path_get(shp,script))) < 0)
+			{
 				errormsg(SH_DICT,ERROR_system(1),e_open,script);
+				UNREACHABLE();
+			}
 			filename = path_fullname(shp,stkptr(shp->stk,PATH_OFFSET));
 		}
 	}
@@ -362,11 +388,17 @@ int    b_shift(register int n, register char *argv[], Shbltin_t *context)
 			return(2);
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 	n = ((arg= *argv)?(int)sh_arith(shp,arg):1);
 	if(n<0 || shp->st.dolc<n)
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_number,arg);
+		UNREACHABLE();
+	}
 	else
 	{
 		shp->st.dolv += n;
@@ -385,10 +417,13 @@ int    b_wait(int n,register char *argv[],Shbltin_t *context)
 			break;
 		case '?':
 			errormsg(SH_DICT,ERROR_usage(2), "%s",opt_info.arg);
-			break;
+			UNREACHABLE();
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 	job_bwait(argv);
 	return(shp->exitval);
@@ -416,20 +451,26 @@ int    b_bg(register int n,register char *argv[],Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s",opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 	if(!sh_isstate(SH_MONITOR))
 	{
 		errormsg(SH_DICT,ERROR_exit(1),e_no_jctl);
-		return(1);
+		UNREACHABLE();
 	}
 	if(flag=='d' && *argv==0)
 		argv = (char**)0;
 	if(job_walk(sfstdout,job_switch,flag,argv))
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_no_job);
+		UNREACHABLE();
+	}
 	return(shp->exitval);
 }
 
@@ -453,15 +494,21 @@ int    b_jobs(register int n,char *argv[],Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s",opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	argv += opt_info.index;
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(*argv==0)
 		argv = (char**)0;
 	if(job_walk(sfstdout,job_list,flag,argv))
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_no_job);
+		UNREACHABLE();
+	}
 	job_wait((pid_t)0);
 	return(shp->exitval);
 }
@@ -527,12 +574,16 @@ int	b_times(int argc, char *argv[], Shbltin_t *context)
 	    case ':':
 		errormsg(SH_DICT, 2, "%s", opt_info.arg);
 		errormsg(SH_DICT, ERROR_usage(2), "%s", optusage((char*)0));
+		UNREACHABLE();
 	    default:
 		errormsg(SH_DICT, ERROR_usage(0), "%s", opt_info.arg);
 		return(2);
 	}
 	if (argv[opt_info.index])
+	{
 		errormsg(SH_DICT, ERROR_exit(2), e_toomanyops);
+		UNREACHABLE();
+	}
 	/* Get & print the times */
 	print_cpu_times();
 	return(0);
@@ -555,21 +606,30 @@ int	b_universe(int argc, char *argv[],Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s",opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	argv += opt_info.index;
 	argc -= opt_info.index;
 	if(error_info.errors || argc>1)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(arg = argv[0])
 	{
 		if(!astconf("UNIVERSE",0,arg))
+		{
 			errormsg(SH_DICT,ERROR_exit(1), e_badname,arg);
+			UNREACHABLE();
+		}
 	}
 	else
 	{
 		if(!(arg=astconf("UNIVERSE",0,0)))
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_nouniverse);
+			UNREACHABLE();
+		}
 		else
 			sfputr(sfstdout,arg,'\n');
 	}

src/cmd/ksh93/bltins/mkservice.c

@@ -421,13 +421,16 @@ int	b_mkservice(int argc, char** argv, Shbltin_t *context)
 			continue;
 		case '?':
 			error(ERROR_usage(2), opt_info.arg);
-			continue;
+			UNREACHABLE();
 		}
 		break;
 	}
 	argv += opt_info.index;
 	if (error_info.errors || !(var = *argv++) || !(path = *argv++) || *argv)
+	{
 		error(ERROR_usage(2), optusage(NiL));
+		UNREACHABLE();
+	}
 	sp = sh_newof(0, Service_t, 1, 0);
 	sp->acceptf = Accept;
 	sp->actionf = Action;
@@ -440,6 +443,7 @@ int	b_mkservice(int argc, char** argv, Shbltin_t *context)
 	{
 		free((void*)sp);
 		error(ERROR_exit(1), "%s: cannot start service", path);
+		UNREACHABLE();
 	}
 	if((sp->fd = fcntl(fd, F_DUPFD, 10))>=10)
 		close(fd);
@@ -472,13 +476,16 @@ int	b_eloop(int argc, char** argv, Shbltin_t *context)
 			continue;
 		case '?':
 			error(ERROR_usage(2), opt_info.arg);
-			continue;
+			UNREACHABLE();
 		}
 		break;
 	}
 	argv += opt_info.index;
 	if (error_info.errors  || *argv)
+	{
 		error(ERROR_usage(2), optusage(NiL));
+		UNREACHABLE();
+	}
 	while(1)
 	{
 		if(waitnotify(-1, timeout, 0)==0)

src/cmd/ksh93/bltins/print.c

@@ -214,7 +214,10 @@ int    b_print(int argc, char *argv[], Shbltin_t *context)
 		case 's':
 			/* print to history file */
 			if(!sh_histinit((void*)shp))
+			{
 				errormsg(SH_DICT,ERROR_system(1),e_history);
+				UNREACHABLE();
+			}
 			fd = sffileno(shp->gd->hist_ptr->histfp);
 			sh_onstate(SH_HISTORY);
 			sflag++;
@@ -266,13 +269,19 @@ int    b_print(int argc, char *argv[], Shbltin_t *context)
 			break;
 		case '?':
 			errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-			break;
+			UNREACHABLE();
 	}
 	argv += opt_info.index;
 	if(error_info.errors || (argc<0 && !(format = *argv++)))
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(vflag && format)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"-%c and -f are mutually exclusive",vflag);
+		UNREACHABLE();
+	}
 skip:
 	if(format)
 		format = genformat(format);
@@ -293,6 +302,7 @@ skip2:
 		if(fd==1)
 			return(1);
 		errormsg(SH_DICT,ERROR_system(1),msg);
+		UNREACHABLE();
 	}
 	if(!(outfile=shp->sftable[fd]))
 	{
@@ -545,7 +555,10 @@ static ssize_t fmtbase64(Sfio_t *iop, char *string, int alt)
 	if(!np || nv_isnull(np))
 	{
 		if(sh_isoption(SH_NOUNSET))
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_notset,string);
+			UNREACHABLE();
+		}
 		return(0);
 	}
 	if(nv_isattr(np,NV_INTEGER))
@@ -755,7 +768,10 @@ static int extend(Sfio_t* sp, void* v, Sffmt_t* fe)
 			break;
 		default:
 			if(!strchr("DdXxoUu",format))
+			{
 				errormsg(SH_DICT,ERROR_exit(1),e_formspec,format);
+				UNREACHABLE();
+			}
 			fe->fmt = 'd';
 			value->ll = 0;
 			break;
@@ -934,7 +950,7 @@ static int extend(Sfio_t* sp, void* v, Sffmt_t* fe)
 			fe->fmt = 'd';
 			fe->size = sizeof(value->ll);
 			errormsg(SH_DICT,ERROR_exit(1),e_formspec,format);
-			break;
+			UNREACHABLE();
 		}
 		if (format == '.')
 			value->i = value->ll;
@@ -980,13 +996,19 @@ static int extend(Sfio_t* sp, void* v, Sffmt_t* fe)
 	case 'P':
 		s = fmtmatch(value->s);
 		if(!s || *s==0)
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_badregexp,value->s);
+			UNREACHABLE();
+		}
 		value->s = s;
 		break;
 	case 'R':
 		s = fmtre(value->s);
 		if(!s || *s==0)
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_badregexp,value->s);
+			UNREACHABLE();
+		}
 		value->s = s;
 		break;
 	case 'Q':

src/cmd/ksh93/bltins/read.c

@@ -109,7 +109,10 @@ int	b_read(int argc,char *argv[], Shbltin_t *context)
 		break;
 	    case 'p':
 		if((fd = shp->cpipe[0])<=0)
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_query);
+			UNREACHABLE();
+		}
 		break;
 	    case 'n': case 'N':
 		flags &= ((1<<D_FLAG)-1);
@@ -129,7 +132,10 @@ int	b_read(int argc,char *argv[], Shbltin_t *context)
 	    case 'u':
 		fd = (int)opt_info.num;
 		if(opt_info.num<0 || opt_info.num>INT_MAX || (fd>=shp->gd->lim.open_max && !sh_iovalidfd(shp,fd)))
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_file,opt_info.arg); /* reject invalid file descriptors */
+			UNREACHABLE();
+		}
 		if(sh_inuse(shp,fd))
 			fd = -1;
 		break;
@@ -141,15 +147,21 @@ int	b_read(int argc,char *argv[], Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	argv += opt_info.index;
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2), "%s", optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(!((r=shp->fdstatus[fd])&IOREAD)  || !(r&(IOSEEK|IONOSEEK)))
 		r = sh_iocheckfd(shp,fd);
 	if(fd<0 || !(r&IOREAD))
+	{
 		errormsg(SH_DICT,ERROR_system(1),e_file+4);
+		UNREACHABLE();
+	}
 	/* look for prompt */
 	if((name = *argv) && (name=strchr(name,'?')) && (r&IOTTY))
 		r = strlen(name++);
@@ -485,7 +497,10 @@ int sh_readline(register Shell_t *shp,char **names, volatile int fd, int flags,s
 	{
 		c = sfvalue(iop)+1;
 		if(!sferror(iop) && sfgetc(iop) >=0)
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_overlimit,"line length");
+			UNREACHABLE();
+		}
 	}
 	if(timeslot)
 		timerdel(timeslot);

src/cmd/ksh93/bltins/regress.c

@@ -270,7 +270,7 @@ int b___regress__(int argc, char** argv, Shbltin_t *context)
 		{
 		case '?':
 			errormsg(SH_DICT, ERROR_usage(2), "%s", opt_info.arg);
-			break;
+			UNREACHABLE();
 		case ':':
 			errormsg(SH_DICT, 2, "%s", opt_info.arg);
 			break;
@@ -332,7 +332,10 @@ int b___regress__(int argc, char** argv, Shbltin_t *context)
 		break;
 	}
 	if (error_info.errors || *(argv + opt_info.index))
+	{
 		errormsg(SH_DICT, ERROR_usage(2), "%s", optusage(NiL));
+		UNREACHABLE();
+	}
 	return 0;
 }
 

src/cmd/ksh93/bltins/sleep.c

@@ -60,10 +60,13 @@ int	b_sleep(register int argc,char *argv[],Shbltin_t *context)
 			break;
 		case '?':
 			errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-			break;
+			UNREACHABLE();
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT, ERROR_usage(2), "%s", optusage(NULL));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 	if(cp = *argv)
 	{
@@ -93,16 +96,25 @@ int	b_sleep(register int argc,char *argv[],Shbltin_t *context)
 					ns = tmxdate(pp, &last, now);
 			}
 			if(*last)
+			{
 				errormsg(SH_DICT,ERROR_exit(1),e_number,*argv);
+				UNREACHABLE();
+			}
 			d = ns - now;
 			d /= TMX_RESOLUTION;
 		}
 skip:
 		if(argv[1])
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_oneoperand);
+			UNREACHABLE();
+		}
 	}
 	else if(!sflag)
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_oneoperand);
+		UNREACHABLE();
+	}
 	if(d > .10)
 	{
 		time(&tloc);

src/cmd/ksh93/bltins/test.c

@@ -141,7 +141,10 @@ int b_test(int argc, char *argv[],Shbltin_t *context)
 	{
 		cp = argv[--argc];
 		if(!c_eq(cp, ']'))
+		{
 			errormsg(SH_DICT,ERROR_exit(2),e_missing,"']'");
+			UNREACHABLE();
+		}
 	}
 	if(argc <= 1)
 	{
@@ -192,6 +195,7 @@ int b_test(int argc, char *argv[],Shbltin_t *context)
 					goto done;
 				}
 				errormsg(SH_DICT,ERROR_exit(2),e_badop,cp);
+				UNREACHABLE();
 			}
 			exitval = (test_binop(tdata.sh,op,argv[1],argv[3])^(argc!=5));
 			goto done;
@@ -218,7 +222,7 @@ int b_test(int argc, char *argv[],Shbltin_t *context)
 					av[2] = 0;
 					optget(av,sh_opttest);
 					errormsg(SH_DICT,ERROR_usage(2), "%s",opt_info.arg);
-					return(2);
+					UNREACHABLE();
 				}
 				break;
 			}
@@ -276,6 +280,7 @@ static int expr(struct test *tp,register int flag)
 		if(flag==0)
 			break;
 		errormsg(SH_DICT,ERROR_exit(2),e_badsyntax);
+		UNREACHABLE();
 	}
 	return(r);
 }
@@ -290,6 +295,7 @@ static char *nxtarg(struct test *tp,int mt)
 			return(0);
 		}
 		errormsg(SH_DICT,ERROR_exit(2),e_argument);
+		UNREACHABLE();
 	}
 	return(tp->av[tp->ap++]);
 }
@@ -308,7 +314,10 @@ static int e3(struct test *tp)
 		op = expr(tp,1);
 		cp = nxtarg(tp,0);
 		if(!cp || !c_eq(cp, ')'))
+		{
 			errormsg(SH_DICT,ERROR_exit(2),e_missing,"')'");
+			UNREACHABLE();
+		}
 		return(op);
 	}
 	cp = nxtarg(tp,1);
@@ -340,6 +349,7 @@ static int e3(struct test *tp)
 			if(op==0 || !strchr(test_opchars+10,op))
 				return(1);
 			errormsg(SH_DICT,ERROR_exit(2),e_argument);
+			UNREACHABLE();
 		}
 		if(strchr(test_opchars,op))
 			return(test_unop(tp->sh,op,cp));
@@ -354,7 +364,10 @@ skip:
 	if(!(op&TEST_BINOP))
 		cp = nxtarg(tp,0);
 	if(!op)
+	{
 		errormsg(SH_DICT,ERROR_exit(2),e_badop,binop);
+		UNREACHABLE();
+	}
 	if(op==TEST_AND || op==TEST_OR)
 		tp->ap--;
 	return(test_binop(tp->sh,op,arg,cp));
@@ -491,8 +504,7 @@ int test_unop(Shell_t *shp,register int op,register const char *arg)
 		static char a[3] = "-?";
 		a[1]= op;
 		errormsg(SH_DICT,ERROR_exit(2),e_badop,a);
-		/* NOTREACHED */
-		return(0);
+		UNREACHABLE();
 	    }
 	}
 }
@@ -553,8 +565,7 @@ int test_binop(Shell_t *shp,register int op,const char *left,const char *right)
 			errormsg(SH_DICT, ERROR_exit(2), op==TEST_END ? e_badop : e_unsupported_op, shtab_testops[i].sh_name);
 		}
 	}
-	/* NOTREACHED */
-	return(0);
+	UNREACHABLE();
 }
 
 /*

src/cmd/ksh93/bltins/trap.c

@@ -60,11 +60,13 @@ int	b_trap(int argc,char *argv[],Shbltin_t *context)
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(0), "%s", opt_info.arg);
 		return(2);
-		break;
 	}
 	argv += opt_info.index;
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s", optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(arg = *argv)
 	{
 		char *action = arg;
@@ -91,7 +93,10 @@ int	b_trap(int argc,char *argv[],Shbltin_t *context)
 				}
 			}
 			if(!argv[0])
+			{
 				errormsg(SH_DICT,ERROR_exit(1),e_condition);
+				UNREACHABLE();
+			}
 		}
 		while(arg = *argv++)
 		{
@@ -217,14 +222,17 @@ int	b_kill(int argc,char *argv[],Shbltin_t *context)
 			break;
 		case '?':
 			errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-			break;
+			UNREACHABLE();
 	}
 endopts:
 	argv += opt_info.index;
 	if(*argv && strcmp(*argv,"--")==0 && strcmp(*(argv-1),"--")!=0)
 		argv++;
 	if(error_info.errors || flag==(L_FLAG|S_FLAG) || (!(*argv) && !(flag&L_FLAG)))
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s", optusage((char*)0));
+		UNREACHABLE();
+	}
 	/* just in case we send a kill -9 $$ */
 	sfsync(sfstderr);
 	if(flag&L_FLAG)
@@ -241,6 +249,7 @@ endopts:
 				{
 					shp->exitval = 2;
 					errormsg(SH_DICT,ERROR_exit(1),e_nosignal,signame);
+					UNREACHABLE();
 				}
 				sfprintf(sfstdout,"%d\n",sig);
 			}
@@ -250,7 +259,10 @@ endopts:
 	if(flag&S_FLAG)
 	{
 		if((sig=sig_number(shp,signame)) < 0 || sig > shp->gd->sigmax)
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_nosignal,signame);
+			UNREACHABLE();
+		}
 	}
 	if(job_walk(sfstdout,job_kill,sig,argv))
 		shp->exitval = 1;
@@ -273,16 +285,28 @@ int	b_suspend(int argc,char *argv[],Shbltin_t *context)
 			break;
 		case '?':
 			errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-			break;
+			UNREACHABLE();
 	}
 	if(error_info.errors)	/* no options supported (except AST --man, etc.) */
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s", optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(argv[opt_info.index])	/* no operands supported */
+	{
 		errormsg(SH_DICT, ERROR_exit(2), e_toomanyops);
+		UNREACHABLE();
+	}
 	if(sh_isoption(SH_LOGIN_SHELL))
+	{
 		errormsg(SH_DICT, ERROR_exit(1), "cannot suspend a login shell");
+		UNREACHABLE();
+	}
 	if(kill(context->shp->gd->pid, SIGSTOP) != 0)
+	{
 		errormsg(SH_DICT, ERROR_exit(1), "could not signal main shell at PID %d", context->shp->gd->pid);
+		UNREACHABLE();
+	}
 	return(0);
 }
 #endif /* defined(JOBS) && defined(SIGSTOP) */

src/cmd/ksh93/bltins/typeset.c

@@ -107,7 +107,10 @@ int    b_readonly(int argc,char *argv[],Shbltin_t *context)
 			return(2);
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),optusage(NIL(char*)));
+		UNREACHABLE();
+	}
 	argv += (opt_info.index-1);
 	if(*command=='r')
 		flag = (NV_ASSIGN|NV_RDONLY|NV_VARNAME);
@@ -166,7 +169,10 @@ int    b_alias(int argc,register char *argv[],Shbltin_t *context)
 			return(2);
 		}
 		if(error_info.errors)
+		{
 			errormsg(SH_DICT,ERROR_usage(2),"%s",optusage(NIL(char*)));
+			UNREACHABLE();
+		}
 		argv += (opt_info.index-1);
 	}
 	/* 'alias -t', 'hash' */
@@ -222,7 +228,10 @@ int    b_typeset(int argc,register char *argv[],Shbltin_t *context)
 		else if(argv[0][0] == 'n')	/* <n>ameref == typeset -n */
 			new_argv[1] = "-n";
 		else
+		{
 			errormsg(SH_DICT, ERROR_exit(128), "internal error");
+			UNREACHABLE();
+		}
 		for (n = 1; n <= argc; n++)
 			new_argv[n + 1] = argv[n];
 		argc++;
@@ -305,7 +314,10 @@ int    b_typeset(int argc,register char *argv[],Shbltin_t *context)
 				if(tdata.argnum==0)
 					tdata.argnum = (int)opt_info.num;
 				if(tdata.argnum < 0)
+				{
 					errormsg(SH_DICT,ERROR_exit(1), e_badfield, tdata.argnum);
+					UNREACHABLE();
+				}
 				isadjust = 1;
 				if(n=='Z')
 					flag |= NV_ZFILL;
@@ -317,7 +329,10 @@ int    b_typeset(int argc,register char *argv[],Shbltin_t *context)
 				break;
 			case 'M':
 				if((tdata.wctname = opt_info.arg) && !nv_mapchar((Namval_t*)0,tdata.wctname))
+				{
 					errormsg(SH_DICT, ERROR_exit(1),e_unknownmap, tdata.wctname);
+					UNREACHABLE();
+				}
 				if(tdata.wctname && strcmp(tdata.wctname,e_tolower)==0)
 					flag |= NV_UTOL;
 				else
@@ -452,9 +467,15 @@ endargs:
 		flag |= NV_STATICF;
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s", optusage(NIL(char*)));
+		UNREACHABLE();
+	}
 	if(sizeof(char*)<8 && tdata.argnum > SHRT_MAX)
+	{
 		errormsg(SH_DICT,ERROR_exit(2),"option argument cannot be greater than %d",SHRT_MAX);
+		UNREACHABLE();
+	}
 	if(isfloat)
 		flag |= NV_DOUBLE;
 	if(sflag)
@@ -496,7 +517,10 @@ endargs:
 #endif /* SHOPT_NAMESPACE */
 		stkseek(stkp,offset);
 		if(!tdata.tp)
+		{
 			errormsg(SH_DICT,ERROR_exit(1),"%s: unknown type",tdata.prefix);
+			UNREACHABLE();
+		}
 		else if(nv_isnull(tdata.tp))
 			nv_newtype(tdata.tp);
 		tdata.tp->nvenv = tdata.help;
@@ -512,7 +536,10 @@ endargs:
 	if(!tdata.sh->mktype)
 		tdata.help = 0;
 	if(tdata.aflag=='+' && (flag&(NV_ARRAY|NV_IARRAY|NV_COMVAR)) && argv[1])
+	{
 		errormsg(SH_DICT,ERROR_exit(1),e_nounattr);
+		UNREACHABLE();
+	}
 	return(setall(argv,flag,troot,&tdata));
 }
 
@@ -632,7 +659,10 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 				{
 					/* Function names cannot be special builtin */
 					if((np=nv_search(name,shp->bltin_tree,0)) && nv_isattr(np,BLT_SPC))
+					{
 						errormsg(SH_DICT,ERROR_exit(1),e_badfun,name);
+						UNREACHABLE();
+					}
 #if SHOPT_NAMESPACE
 					if(shp->namespace)
 						np = sh_fsearch(shp,name,NV_ADD|HASH_NOSCOPE);
@@ -705,7 +735,10 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 			if(nv_isnull(np) && !nv_isarray(np) && nv_isattr(np,NV_NOFREE))
 				nv_offattr(np,NV_NOFREE);
 			else if(tp->tp && !nv_isattr(np,NV_MINIMAL|NV_EXPORT) && (mp=(Namval_t*)np->nvenv) && (ap=nv_arrayptr(mp)) && (ap->nelem&ARRAY_TREE))
+			{
 				errormsg(SH_DICT,ERROR_exit(1),e_typecompat,nv_name(np));
+				UNREACHABLE();
+			}
 			else if((ap=nv_arrayptr(np)) && nv_aindex(np)>0 && ap->nelem==1 && nv_getval(np)==Empty)
 			{
 				ap->nelem++;
@@ -713,7 +746,10 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 				ap->nelem--;
 			}
 			else if(iarray && ap && ap->fun) 
+			{
 				errormsg(SH_DICT,ERROR_exit(1),"cannot change associative array %s to indexed array",nv_name(np));
+				UNREACHABLE();
+			}
 			else if( (iarray||(flag&NV_ARRAY)) && nv_isvtree(np) && !nv_type(np))
 				_nv_unset(np,NV_EXPORT);
 			if(tp->pflag)
@@ -804,7 +840,10 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 				Namfun_t *fp;
 				char  *cp;
 				if(!tp->wctname)
+				{
 					errormsg(SH_DICT,ERROR_exit(1),e_mapchararg,nv_name(np));
+					UNREACHABLE();
+				}
 				cp = (char*)nv_mapchar(np,0);
 				if(fp=nv_mapchar(np,tp->wctname))
 				{
@@ -828,7 +867,10 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 			if (tp->aflag == '-')
 			{
 				if((flag&NV_EXPORT) && (strchr(name,'.') || nv_isvtree(np)))
+				{
 					errormsg(SH_DICT,ERROR_exit(1),e_badexport,name);
+					UNREACHABLE();
+				}
 #if SHOPT_BSH
 				if(flag&NV_EXPORT)
 					nv_offattr(np,NV_IMPORT);
@@ -849,7 +891,10 @@ static int     setall(char **argv,register int flag,Dt_t *troot,struct tdata *tp
 			else
 			{
 				if((flag&NV_RDONLY) && (curflag&NV_RDONLY))
+				{
 					errormsg(SH_DICT,ERROR_exit(1),e_readonly,nv_name(np));
+					UNREACHABLE();
+				}
 				newflag = curflag & ~flag;
 			}
 			if (tp->aflag && (tp->argnum || (curflag!=newflag)))
@@ -1071,18 +1116,27 @@ int	b_builtin(int argc,char *argv[],Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	argv += opt_info.index;
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s", optusage(NIL(char*)));
+		UNREACHABLE();
+	}
 	if(arg || *argv)
 	{
 		if(sh_isoption(SH_RESTRICTED))
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_restricted,argv[-opt_info.index]);
+			UNREACHABLE();
+		}
 #if SHOPT_PFSH
 		if(sh_isoption(SH_PFSH))
+		{
 			errormsg(SH_DICT,ERROR_exit(1),e_pfsh,argv[-opt_info.index]);
+			UNREACHABLE();
+		}
 #endif
 		if(tdata.sh->subshell && !tdata.sh->subshare)
 			sh_subfork();
@@ -1244,7 +1298,10 @@ static int unall(int argc, char **argv, register Dt_t *troot, Shell_t* shp)
 	}
 	argv += opt_info.index;
 	if(error_info.errors || (*argv==0 &&!all))
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage(NIL(char*)));
+		UNREACHABLE();
+	}
 	if(!troot)
 		return(1);
 	r = 0;

src/cmd/ksh93/bltins/ulimit.c

@@ -44,7 +44,7 @@
 		NOT_USED(argv);
 		NOT_USED(context);
 		errormsg(SH_DICT,ERROR_exit(2),e_nosupport);
-		return(0);
+		UNREACHABLE();
 	}
 #else
 
@@ -106,7 +106,7 @@ int	b_ulimit(int argc,char *argv[],Shbltin_t *context)
 			break;
 		case '?':
 			errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-			break;
+			UNREACHABLE();
 	}
 	opt_info.disc = 0;
 	/* default to -f */
@@ -121,7 +121,10 @@ int	b_ulimit(int argc,char *argv[],Shbltin_t *context)
 	/* only one option at a time for setting */
 	label = (hit&(hit-1));
 	if(error_info.errors || (limit && label) || argc>opt_info.index+1)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),optusage((char*)0));
+		UNREACHABLE();
+	}
 	if(mode==0)
 		mode = (HARD|SOFT);
 	for(tp = shtab_limits; tp->option && hit; tp++,hit>>=1)
@@ -145,26 +148,41 @@ int	b_ulimit(int argc,char *argv[],Shbltin_t *context)
 				else if((i=strton(limit,&last,NiL,0))==INFINITY || *last)
 				{
 					if((i=sh_strnum(limit,&last,2))==INFINITY || *last)
+					{
 						errormsg(SH_DICT,ERROR_system(1),e_number,limit);
+						UNREACHABLE();
+					}
 					i *= unit;
 				}
 			}
 			if(nosupport)
+			{
 				errormsg(SH_DICT,ERROR_system(1),e_readonly,tp->name);
+				UNREACHABLE();
+			}
 			else
 			{
 #ifdef _lib_getrlimit
 				if(getrlimit(n,&rlp) <0)
+				{
 					errormsg(SH_DICT,ERROR_system(1),e_number,limit);
+					UNREACHABLE();
+				}
 				if(mode&HARD)
 					rlp.rlim_max = i;
 				if(mode&SOFT)
 					rlp.rlim_cur = i;
 				if(setrlimit(n,&rlp) <0)
+				{
 					errormsg(SH_DICT,ERROR_system(1),e_overlimit,limit);
+					UNREACHABLE();
+				}
 #else
 				if((i=vlimit(n,i)) < 0)
+				{
 					errormsg(SH_DICT,ERROR_system(1),e_number,limit);
+					UNREACHABLE();
+				}
 #endif /* _lib_getrlimit */
 			}
 		}
@@ -174,7 +192,10 @@ int	b_ulimit(int argc,char *argv[],Shbltin_t *context)
 			{
 #ifdef  _lib_getrlimit
 				if(getrlimit(n,&rlp) <0)
+				{
 					errormsg(SH_DICT,ERROR_system(1),e_number,limit);
+					UNREACHABLE();
+				}
 				if(mode&HARD)
 					i = rlp.rlim_max;
 				if(mode&SOFT)
@@ -185,7 +206,10 @@ int	b_ulimit(int argc,char *argv[],Shbltin_t *context)
 #   endif /* _lib_ulimit */
 				i = -1;
 				if((i=vlimit(n,i)) < 0)
+				{
 					errormsg(SH_DICT,ERROR_system(1),e_number,limit);
+					UNREACHABLE();
+				}
 #endif /* _lib_getrlimit */
 			}
 			if(label)

src/cmd/ksh93/bltins/umask.c

@@ -53,10 +53,13 @@ int	b_umask(int argc,char *argv[],Shbltin_t *context)
 			break;
 		case '?':
 			errormsg(SH_DICT,ERROR_usage(2), "%s",opt_info.arg);
-			break;
+			UNREACHABLE();
 	}
 	if(error_info.errors)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
+		UNREACHABLE();
+	}
 	argv += opt_info.index;
 	if(mask = *argv)
 	{
@@ -68,7 +71,10 @@ int	b_umask(int argc,char *argv[],Shbltin_t *context)
 				if (c>='0' && c<='7')	
 					flag = (flag<<3) + (c-'0');	
 				else
+				{
 					errormsg(SH_DICT,ERROR_exit(1),e_number,*argv);
+					UNREACHABLE();
+				}
 			}
 		}
 		else
@@ -80,6 +86,7 @@ int	b_umask(int argc,char *argv[],Shbltin_t *context)
 			{
 				umask(flag);
 				errormsg(SH_DICT,ERROR_exit(1),e_format,mask);
+				UNREACHABLE();
 			}
 			flag = (~c&0777);
 		}

src/cmd/ksh93/bltins/whence.c

@@ -58,7 +58,10 @@ int	b_command(register int argc,char *argv[],Shbltin_t *context)
 	{
 	    case 'p':
 		if(sh_isoption(SH_RESTRICTED))
+		{
 			 errormsg(SH_DICT,ERROR_exit(1),e_restricted,"-p");
+			 UNREACHABLE();
+		}
 		sh_onstate(SH_DEFPATH);
 		break;
 	    case 'v':
@@ -79,7 +82,7 @@ int	b_command(register int argc,char *argv[],Shbltin_t *context)
 		if(argc==0)
 			return(0);
 		errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	if(argc==0)
 	{
@@ -91,7 +94,10 @@ int	b_command(register int argc,char *argv[],Shbltin_t *context)
 	}
 	argv += opt_info.index;
 	if(error_info.errors || !*argv)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s", optusage((char*)0));
+		UNREACHABLE();
+	}
 	return(whence(shp,argv, flags));
 }
 
@@ -128,11 +134,14 @@ int	b_whence(int argc,char *argv[],Shbltin_t *context)
 		break;
 	    case '?':
 		errormsg(SH_DICT,ERROR_usage(2), "%s", opt_info.arg);
-		break;
+		UNREACHABLE();
 	}
 	argv += opt_info.index;
 	if(error_info.errors || !*argv)
+	{
 		errormsg(SH_DICT,ERROR_usage(2),optusage((char*)0));
+		UNREACHABLE();
+	}
 	return(whence(shp, argv, flags));
 }