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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>
This commit is contained in:
Johnothan King
GitHub
parent
56913f8c2a
commit
c4f980eb29
87 changed files with 1170 additions and 122 deletions
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@ -510,6 +510,11 @@ static int outexcept(register Sfio_t *iop,int type,void *data,Sfdisc_t *handle)
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sfpurge(iop);
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sfpool(iop,NIL(Sfio_t*),SF_WRITE);
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errno = save;
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/*
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* Note: UNREACHABLE() is avoided here because this errormsg() call will return.
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* The ERROR_system flag causes sh_exit() to be called, but if shp->jmplist->mode
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* is 0 (see above), then sh_exit() neither exits nor longjmps. See fault.c.
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*/
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errormsg(SH_DICT,ERROR_system(1),e_badwrite,sffileno(iop));
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active = 0;
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((struct checkpt*)shp->jmplist)->mode = mode;
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@ -616,6 +621,7 @@ static void io_preserve(Shell_t* shp, register Sfio_t *sp, register int f2)
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shp->toomany = 1;
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((struct checkpt*)shp->jmplist)->mode = SH_JMPERREXIT;
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errormsg(SH_DICT,ERROR_system(1),e_toomany);
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UNREACHABLE();
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}
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if(f2 >= shp->gd->lim.open_max)
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sh_iovalidfd(shp,f2);
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@ -669,7 +675,10 @@ int sh_iorenumber(Shell_t *shp, register int f1,register int f2)
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{
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shp->fdstatus[f2] = (shp->fdstatus[f1]&~IOCLEX);
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if((f2 = sh_fcntl(f1,F_DUPFD, f2)) < 0)
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{
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errormsg(SH_DICT,ERROR_system(1),e_file+4);
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UNREACHABLE();
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}
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else if(f2 <= 2)
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sh_iostream(shp,f2);
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}
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@ -872,7 +881,10 @@ int sh_chkopen(register const char *name)
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{
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register int fd = sh_open(name,O_RDONLY,0);
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if(fd < 0)
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{
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errormsg(SH_DICT,ERROR_system(1),e_open,name);
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UNREACHABLE();
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}
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return(fd);
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}
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@ -902,7 +914,10 @@ int sh_pipe(register int pv[])
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Shell_t *shp = sh_getinterp();
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int fd[2];
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if(pipe(fd)<0 || (pv[0]=fd[0])<0 || (pv[1]=fd[1])<0)
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{
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errormsg(SH_DICT,ERROR_system(1),e_pipe);
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UNREACHABLE();
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}
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pv[0] = sh_iomovefd(pv[0]);
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pv[1] = sh_iomovefd(pv[1]);
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shp->fdstatus[pv[0]] = IONOSEEK|IOREAD;
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@ -925,7 +940,10 @@ int sh_pipe(register int pv[])
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Shell_t *shp = sh_getinterp();
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int fd[2];
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if(pipe(fd)<0 || (pv[0]=fd[0])<0 || (pv[1]=fd[1])<0)
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{
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errormsg(SH_DICT,ERROR_system(1),e_pipe);
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UNREACHABLE();
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}
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pv[0] = sh_iomovefd(pv[0]);
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pv[1] = sh_iomovefd(pv[1]);
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shp->fdstatus[pv[0]] = IONOSEEK|IOREAD;
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@ -1118,7 +1136,10 @@ int sh_redirect(Shell_t *shp,struct ionod *iop, int flag)
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if(fn==1)
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{
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if(shp->subshare && flag==2)
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{
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errormsg(SH_DICT,ERROR_exit(1),"cannot redirect stdout inside shared-state comsub");
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UNREACHABLE();
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}
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if(shp->subshell && (flag==2 || isstring))
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sh_subfork();
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}
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@ -1170,13 +1191,19 @@ int sh_redirect(Shell_t *shp,struct ionod *iop, int flag)
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{
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np = nv_open(iop->iovname,shp->var_tree,NV_NOASSIGN|NV_VARNAME);
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if(nv_isattr(np,NV_RDONLY))
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{
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errormsg(SH_DICT,ERROR_exit(1),e_readonly, nv_name(np));
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UNREACHABLE();
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}
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io_op[0] = '}';
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if((iof&IOLSEEK) || ((iof&IOMOV) && *fname=='-'))
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fn = nv_getnum(np);
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}
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if(fn>=shp->gd->lim.open_max && !sh_iovalidfd(shp,fn))
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{
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errormsg(SH_DICT,ERROR_system(1),e_file+4);
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UNREACHABLE();
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}
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if(iof&IOLSEEK)
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{
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io_op[2] = '#';
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@ -1272,7 +1299,10 @@ int sh_redirect(Shell_t *shp,struct ionod *iop, int flag)
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else if(iof&IORDW)
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{
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if(sh_isoption(SH_RESTRICTED))
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{
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errormsg(SH_DICT,ERROR_exit(1),e_restricted,fname);
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UNREACHABLE();
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}
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io_op[2] = '>';
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o_mode = O_RDWR|O_CREAT;
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if(iof&IOREWRITE)
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@ -1286,7 +1316,10 @@ int sh_redirect(Shell_t *shp,struct ionod *iop, int flag)
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fd=sh_chkopen(fname);
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}
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else if(sh_isoption(SH_RESTRICTED))
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{
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errormsg(SH_DICT,ERROR_exit(1),e_restricted,fname);
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UNREACHABLE();
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}
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else
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{
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if(iof&IOAPP)
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@ -1315,6 +1348,7 @@ int sh_redirect(Shell_t *shp,struct ionod *iop, int flag)
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{
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errno = EEXIST;
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errormsg(SH_DICT,ERROR_system(1),e_exists,fname);
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UNREACHABLE();
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}
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}
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else
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@ -1325,7 +1359,10 @@ int sh_redirect(Shell_t *shp,struct ionod *iop, int flag)
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if(flag!=SH_SHOWME)
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{
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if((fd=sh_open(tname?tname:fname,o_mode,RW_ALL)) <0)
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{
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errormsg(SH_DICT,ERROR_system(1),((o_mode&O_CREAT)?e_create:e_open),fname);
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UNREACHABLE();
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}
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if(perm>0)
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#if _lib_fchmod
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fchmod(fd,perm);
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@ -1507,8 +1544,7 @@ int sh_redirect(Shell_t *shp,struct ionod *iop, int flag)
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return(indx);
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fail:
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errormsg(SH_DICT,ERROR_system(1),message,fname);
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/* NOTREACHED */
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return(0);
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UNREACHABLE();
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}
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/*
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* Create a tmp file for the here-document
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@ -1522,7 +1558,10 @@ static int io_heredoc(Shell_t *shp,register struct ionod *iop, const char *name,
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return(sh_open(e_devnull,O_RDONLY));
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/* create an unnamed temporary file */
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if(!(outfile=sftmp(0)))
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{
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errormsg(SH_DICT,ERROR_system(1),e_tmpcreate);
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UNREACHABLE();
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}
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if(iop->iofile&IOSTRG)
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{
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if(traceon)
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@ -1656,6 +1695,7 @@ void sh_iosave(Shell_t *shp, register int origfd, int oldtop, char *name)
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shp->toomany=1;
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((struct checkpt*)shp->jmplist)->mode = SH_JMPERREXIT;
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errormsg(SH_DICT,ERROR_system(1),e_toomany);
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UNREACHABLE();
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}
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}
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filemap[shp->topfd].tname = name;
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@ -2643,7 +2683,10 @@ Sfio_t *sh_pathopen(const char *cp)
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n = path_open(shp,cp,"");
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#endif
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if(n < 0)
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{
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errormsg(SH_DICT,ERROR_system(1),e_open,cp);
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UNREACHABLE();
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}
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return(sh_iostream(shp,n));
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}
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