main: quote output file name before passing it to system(3) function

Following command line doesn't work:

      $ ctags -o 'a b' ...

because a shell lauched from system(3) deals a whitespace between 'a'
and 'b' as a separator. The output file name is passed to system(3)
to run external sort command.

This commit adds code to put double and single quoets around the output
file name before passing it to system(3).

The issue is reported by Lorenz Hipp <lhipp@idealbonn.de> in a private mail.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>

Tmain/abnormal-output-file-names.d/input.c

@@ -0,0 +1 @@
+int x;

Tmain/abnormal-output-file-names.d/run.sh

@@ -0,0 +1,39 @@
+# Copyright: 2016 Masatake YAMATO
+# License: GPL-2
+
+CTAGS=$1
+
+rm -f ./"'"
+rm -f ./'"'
+rm -f ./'$(ls)'
+rm -f ./'a b'
+
+${CTAGS} --quiet --options=NONE -o ./"'" --extra=-pF input.c
+${CTAGS} --quiet --options=NONE -o ./'"' --extra=-pF input.c
+${CTAGS} --quiet --options=NONE -o ./'$(ls)' --extra=-pF input.c
+${CTAGS} --quiet --options=NONE -o ./'a b' --extra=-pF input.c
+
+echo '#' SINGLE QUOTE
+if [ -e "'" ]; then
+	cat "'"
+fi
+
+echo '#' DOUBLE QUOTES
+if [ -e '"' ]; then
+	cat '"'
+fi
+
+echo '#' PROCESS SUBSTITUTION
+if [ -e '$(ls)' ]; then
+	cat '$(ls)'
+fi
+
+echo '#' SPACE
+if [ -e 'a b' ]; then
+	cat 'a b'
+fi
+
+rm -f ./"'"
+rm -f ./'"'
+rm -f ./'$(ls)'
+rm -f ./'a b'

Tmain/abnormal-output-file-names.d/stdout-expected.txt

@@ -0,0 +1,8 @@
+# SINGLE QUOTE
+x	input.c	/^int x;$/;"	v	typeref:typename:int
+# DOUBLE QUOTES
+x	input.c	/^int x;$/;"	v	typeref:typename:int
+# PROCESS SUBSTITUTION
+x	input.c	/^int x;$/;"	v	typeref:typename:int
+# SPACE
+x	input.c	/^int x;$/;"	v	typeref:typename:int

main/sort.c

@@ -55,17 +55,44 @@ extern void catFile (MIO *mio)
 # define PE_CONST const
 #endif
 
+/*
+   Output file name should not be evaluated in system(3) function.
+   The name must be used as is. Quotations are required to block the
+   evaluation.
+
+   Normal single-quotes are used to quote a cstring:
+   a => 'a'
+   " => '"'
+
+   If a single-quote is included in the cstring, use double quotes for quoting it.
+   ' => ''"'"''
+*/
+static void appendCstringWithQuotes (vString *dest, const char* cstr)
+{
+	const char* o;
+
+	vStringPut (dest, '\'');
+	for (o = cstr; *o; o++)
+	{
+		if (*o == '\'')
+			vStringCatS (dest, "'\"'\"'");
+		else
+			vStringPut (dest, *o);
+	}
+	vStringPut (dest, '\'');
+}
+
 extern void externalSortTags (const bool toStdout, MIO *tagFile)
 {
 	const char *const sortNormalCommand = "sort -u";
 	const char *const sortFoldedCommand = "sort -u -f";
 	const char *sortCommand =
 		Option.sorted == SO_FOLDSORTED ? sortFoldedCommand : sortNormalCommand;
+# ifndef HAVE_SETENV
 	PE_CONST char *const sortOrder1 = "LC_COLLATE=C";
 	PE_CONST char *const sortOrder2 = "LC_ALL=C";
-	const size_t length = 4 + strlen (sortOrder1) + strlen (sortOrder2) +
-			strlen (sortCommand) + (2 * strlen (tagFileName ()));
-	char *const cmd = (char *) malloc (length + 1);
+# endif
+	vString *cmd = vStringNew ();
 	int ret = -1;
 
 	if (cmd != NULL)
@@ -80,19 +107,29 @@ extern void externalSortTags (const bool toStdout, MIO *tagFile)
 		putenv (sortOrder1);
 		putenv (sortOrder2);
 # endif
-		if (toStdout)
-			sprintf (cmd, "%s", sortCommand);
-		else
-			sprintf (cmd, "%s -o %s %s", sortCommand,
-					tagFileName (), tagFileName ());
+		vStringCatS (cmd, sortCommand);
+		if (! toStdout)
+		{
+			vStringCatS (cmd, " -o ");
+			appendCstringWithQuotes (cmd, tagFileName ());
+			vStringPut (cmd, ' ');
+			appendCstringWithQuotes (cmd, tagFileName ());
+		}
 #else
-		if (toStdout)
-			sprintf (cmd, "%s %s %s", sortOrder1, sortOrder2, sortCommand);
-		else
-			sprintf (cmd, "%s %s %s -o %s %s", sortOrder1, sortOrder2,
-					sortCommand, tagFileName (), tagFileName ());
+		vStringCatS (cmd, sortOrder1);
+		vStringPut (cmd, ' ');
+		vStringCatS (cmd, sortOrder2);
+		vStringPut (cmd, ' ');
+		vStringCatS (cmd, sortCommand);
+		if (! toStdout)
+		{
+			vStringCats (cmd, " -o ");
+			appendCstringWithQuotes (cmd, tagFileName ());
+			vStringPut (cmd, ' ');
+			appendCstringWithQuotes (cmd, tagFileName ());
+		}
 #endif
-		verbose ("system (\"%s\")\n", cmd);
+		verbose ("system (\"%s\")\n", vStringValue (cmd));
 		if (toStdout)
 		{
 			const int fdstdin = 0;
@@ -105,15 +142,14 @@ extern void externalSortTags (const bool toStdout, MIO *tagFile)
 				error (FATAL | PERROR, "cannot redirect stdin");
 			if (lseek (fdstdin, 0, SEEK_SET) != 0)
 				error (FATAL | PERROR, "cannot rewind tag file");
-			ret = system (cmd);
+			ret = system (vStringValue (cmd));
 			if (dup2 (fdsave, fdstdin) < 0)
 				error (FATAL | PERROR, "cannot restore stdin fd");
 			close (fdsave);
 		}
 		else
-			ret = system (cmd);
-		free (cmd);
-
+			ret = system (vStringValue (cmd));
+		vStringDelete (cmd);
 	}
 	if (ret != 0)
 		error (FATAL | PERROR, "cannot sort tag file");