shcomp: refuse to write binary data to terminal

So, shcomp has messed up my terminal once too often by writing
compiled binary data to it. While fixing that I've done some other
tweaks as well.

src/cmd/ksh93/sh/shcomp.c: main():
- Fix error/warning message id (the "name:" prefix before messages)
  so it makes sense to the user. Save shcomp's argv[0] id for error
  messages that are directly from shcomp's main(), and use the
  argv[1] script id (set by sh_init()) for warnings produced by the
  compilation process. If there is no script id because we're
  reading from stdin, set it to "(stdin)".
- If no arguments are given, refuse to read from standard input if
  it's on a tty. Instead, write a brief usage message (with pointer
  to --help and --man, see e21a053e) and exit. This is far more
  helpful; people will rarely want to compile a script by manually
  typing it in. If you really want to do that, use /dev/stdin as
  the input filename. :)
- Error out if we're about to write binary data to a tty (even if
  /dev/stdout was given as the output filename).
- Turn off SH_MULTILINE to avoid some pointless editor init in case
  we're reading from stdin on a terminal.
- Do not attempt to copy remaining data if we're already at EOF.
  This fixes a bug that required the user to press Ctrl+D twice
  when manually entering a script on the terminal. Pressing Ctrl+D
  once and then entering more data would corrupt the bytecode.

src/cmd/ksh93/sh/shcomp.c

@@ -37,18 +37,23 @@ static const char usage[] =
 "[-license?http://www.eclipse.org/org/documents/epl-v10.html]"
 "[--catalog?" SH_DICT "]"
 "[+NAME?shcomp - compile a shell script]"
-"[+DESCRIPTION?Unless \b-D\b is specified, \bshcomp\b takes a shell script, "
+"[+DESCRIPTION?Unless \b-D\b is specified, \b\f?\f\b takes a shell script, "
 	"\ainfile\a, and creates a binary format file, \aoutfile\a, that "
 	"\bksh\b can read and execute with the same effect as the original "
 	"script.]"
 "[+?Since aliases are processed as the script is read, alias definitions "
 	"whose value requires variable expansion will not work correctly.]"
 "[+?If \b-D\b is specified, all double quoted strings that are preceded by "
-	"\b$\b are output.  These are the messages that need to be "
+	"\b$\b are output. These are the messages that need to be "
 	"translated to locale specific versions for internationalization.]"
+"[+?If \ainfile\a is a simple command name, the shell script will be searched "
+	"on \b$PATH\b. It does not need execute permission to be found.]"
 "[+?If \aoutfile\a is omitted, then the results will be written to "
-	"standard output.  If \ainfile\a is also omitted, the shell script "
+	"standard output. If \ainfile\a is also omitted, the shell script "
-	"will be read from standard input.]"
+	"will be read from standard input. However, \b\f?\f\b will not read "
+	"a script from your keyboard unless \ainfile\a is given as "
+	"\b/dev/stdin\b, and will refuse to write binary data to a terminal "
+	"in any case.]"
 "[D:dictionary?Generate a list of strings that need to be placed in a message "
 	"catalog for internationalization.]"
 "[n:noexec?Displays warning messages for obsolete or non-conforming "
@@ -67,8 +72,10 @@ static const char usage[] =
 
 #include	<shell.h>
 #include	"defs.h"
+#include	"path.h"
 #include	"shnodes.h"
 #include	"sys/stat.h"
+#include	"terminal.h"
 
 #define CNTL(x)	((x)&037)
 static const char header[6] = { CNTL('k'),CNTL('s'),CNTL('h'),0,SHCOMP_HDR_VERSION,0 };
@@ -79,9 +86,9 @@ int main(int argc, char *argv[])
 	Shell_t	*shp;
 	Namval_t *np;
 	Shnode_t *t;
-	char *cp;
+	char *cp, *shcomp_id, *script_id;
 	int n, nflag=0, vflag=0, dflag=0;
-	error_info.id = argv[0];
+	shcomp_id = error_info.id = path_basename(argv[0]);
 	while(n = optget(argv, usage )) switch(n)
 	{
 	    case 'D':
@@ -101,9 +108,16 @@ int main(int argc, char *argv[])
 		UNREACHABLE();
 	}
 	shp = sh_init(argc,argv,(Shinit_f)0);
+	script_id = error_info.id;  /* set by sh_init() */
+	error_info.id = shcomp_id;
 	shp->shcomp = 1;
 	argv += opt_info.index;
 	argc -= opt_info.index;
+	if(argc==0 && tty_check(0))
+	{
+		errormsg(SH_DICT,ERROR_exit(0),"refusing to read script from terminal",cp);
+		error_info.errors++;
+	}
 	if(error_info.errors || argc>2)
 	{
 		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage((char*)0));
@@ -115,7 +129,10 @@ int main(int argc, char *argv[])
 		in = sh_pathopen(cp);
 	}
 	else
+	{
+		script_id = "(stdin)";
 		in = sfstdin;
+	}
 	if(cp= *argv)
 	{
 		struct stat statb;
@@ -129,6 +146,11 @@ int main(int argc, char *argv[])
 	}
 	else
 		out = sfstdout;
+	if(tty_check(sffileno(out)))
+	{
+		errormsg(SH_DICT,ERROR_exit(1),"refusing to write binary data to terminal",cp);
+		UNREACHABLE();
+	}
 	if(dflag)
 	{
 		sh_onoption(SH_DICTIONARY);
@@ -140,10 +162,12 @@ int main(int argc, char *argv[])
 		sh_onoption(SH_VERBOSE);
 	if(!dflag)
 		sfwrite(out,header,sizeof(header));
+	sh_offoption(SH_MULTILINE);
 	shp->inlineno = 1;
 #if SHOPT_BRACEPAT
         sh_onoption(SH_BRACEEXPAND);
 #endif
+	error_info.id = script_id;
 	while(1)
 	{
 		stakset((char*)0,0);
@@ -153,6 +177,7 @@ int main(int argc, char *argv[])
 				sh_exec(t,0);
 			if(!dflag && sh_tdump(out,t) < 0)
 			{
+				error_info.id = shcomp_id;
 				errormsg(SH_DICT,ERROR_exit(1),"dump failed");
 				UNREACHABLE();
 			}
@@ -161,6 +186,7 @@ int main(int argc, char *argv[])
 			break;
 		if(sferror(in))
 		{
+			error_info.id = shcomp_id;
 			errormsg(SH_DICT,ERROR_system(1),"I/O error");
 			UNREACHABLE();
 		}
@@ -186,7 +212,8 @@ int main(int argc, char *argv[])
 		}
 	}
 	/* copy any remaining input */
-	sfmove(in,out,SF_UNBOUND,-1);
+	if(!sfeof(in))
+		sfmove(in,out,SF_UNBOUND,-1);
 	if(in!=sfstdin)
 		sfclose(in);
 	if(out!=sfstdout)