sed(1): Don't force a newline on last line, if input stream doesn't have one

While here, change how we check if the current line is the last one.
Before, we just checked if there were more files after the current one.
Now, we check the actual content of those files: they files may not have
a line at all. This matches the definition of the "last line" by the
Open Group.

The new behavior is closer to GNU sed.

PR:		160745
Phabric:	https://phabric.freebsd.org/D431
Reviewed by:	jilles
Approved by:	jilles
Exp-run by:	antoine

usr.bin/sed/defs.h

@@ -143,6 +143,7 @@ typedef struct {
 	char *space;		/* Current space pointer. */
 	size_t len;		/* Current length. */
 	int deleted;		/* If deleted. */
+	int append_newline;	/* If originally terminated by \n. */
 	char *back;		/* Backing memory. */
 	size_t blen;		/* Backing memory length. */
 } SPACE;

usr.bin/sed/main.c

@@ -439,8 +439,14 @@ mf_fgets(SPACE *sp, enum e_spflag spflag)
 	len = getline(&p, &plen, infile);
 	if (len == -1)
 		err(1, "%s", fname);
-	if (len != 0 && p[len - 1] == '\n')
+	if (len != 0 && p[len - 1] == '\n') {
+		sp->append_newline = 1;
 		len--;
+	} else if (!lastline()) {
+		sp->append_newline = 1;
+	} else {
+		sp->append_newline = 0;
+	}
 	cspace(sp, p, len, spflag);
 
 	linenum++;
@@ -481,15 +487,49 @@ add_file(char *s)
 	fl_nextp = &fp->next;
 }
 
+static int
+next_files_have_lines()
+{
+	struct s_flist *file;
+	FILE *file_fd;
+	int ch;
+
+	file = files;
+	while ((file = file->next) != NULL) {
+		if ((file_fd = fopen(file->fname, "r")) == NULL)
+			continue;
+
+		if ((ch = getc(file_fd)) != EOF) {
+			/*
+			 * This next file has content, therefore current
+			 * file doesn't contains the last line.
+			 */
+			ungetc(ch, file_fd);
+			fclose(file_fd);
+			return (1);
+		}
+
+		fclose(file_fd);
+	}
+
+	return (0);
+}
+
 int
 lastline(void)
 {
 	int ch;
 
-	if (files->next != NULL && (inplace == NULL || ispan))
-		return (0);
-	if ((ch = getc(infile)) == EOF)
-		return (1);
+	if (feof(infile)) {
+		return !(
+		    (inplace == NULL || ispan) &&
+		    next_files_have_lines());
+	}
+	if ((ch = getc(infile)) == EOF) {
+		return !(
+		    (inplace == NULL || ispan) &&
+		    next_files_have_lines());
+	}
 	ungetc(ch, infile);
 	return (0);
 }

usr.bin/sed/process.c

@@ -63,6 +63,7 @@ static SPACE HS, PS, SS, YS;
 #define	pd		PS.deleted
 #define	ps		PS.space
 #define	psl		PS.len
+#define	psanl		PS.append_newline
 #define	hs		HS.space
 #define	hsl		HS.len
 
@@ -85,7 +86,10 @@ static regex_t *defpreg;
 size_t maxnsub;
 regmatch_t *match;
 
-#define OUT() do {fwrite(ps, 1, psl, outfile); fputc('\n', outfile);} while (0)
+#define OUT() do {							\
+	fwrite(ps, 1, psl, outfile);					\
+	if (psanl) fputc('\n', outfile);				\
+} while (0)
 
 void
 process(void)
@@ -94,6 +98,7 @@ process(void)
 	SPACE tspace;
 	size_t oldpsl = 0;
 	char *p;
+	int oldpsanl;
 
 	p = NULL;
 
@@ -190,11 +195,15 @@ process(void)
 					break;
 				if ((p = memchr(ps, '\n', psl)) != NULL) {
 					oldpsl = psl;
+					oldpsanl = psanl;
 					psl = p - ps;
+					psanl = 1;
 				}
 				OUT();
-				if (p != NULL)
+				if (p != NULL) {
 					psl = oldpsl;
+					psanl = oldpsanl;
+				}
 				break;
 			case 'q':
 				if (!nflag && !pd)
@@ -244,6 +253,7 @@ process(void)
 					cspace(&HS, "", 0, REPLACE);
 				tspace = PS;
 				PS = HS;
+				psanl = tspace.append_newline;
 				HS = tspace;
 				break;
 			case 'y':
@@ -452,6 +462,7 @@ substitute(struct s_command *cp)
 	 */
 	tspace = PS;
 	PS = SS;
+	psanl = tspace.append_newline;
 	SS = tspace;
 	SS.space = SS.back;
 
@@ -521,6 +532,7 @@ do_tr(struct s_tr *y)
 		/* Swap the translation space and the pattern space. */
 		tmp = PS;
 		PS = YS;
+		psanl = tmp.append_newline;
 		YS = tmp;
 		YS.space = YS.back;
 	}

usr.bin/sed/tests/regress.y.out

@@ -1 +1 @@
-fOO
+fOO