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cc1: Improve addinput() and delinput()

There were several problems with these functions:

	- The actions of hiding and unhiding were not isolated,
	  making difficult to identify them.
	- It was a bit difficult to understand how the location
	  was updated in addinput().
	- There was a memory leak in delinput() because the
	  actual input structure was not freed.

--- a/src/cmd/cc/cc1/cc1.h

+++ b/src/cmd/cc/cc1/cc1.h

@@ -396,7 +396,7 @@

 	unsigned lineno;

 	char *filenam;

 	FILE *fp;

-	Symbol *hide;

+	Symbol *macro;

 	char *line, *begin, *p;

 	struct input *next;

 };

--- a/src/cmd/cc/cc1/lex.c

+++ b/src/cmd/cc/cc1/lex.c

@@ -41,8 +41,24 @@

 	lineno = input->lineno = line;

 }

+static void

+hide(Symbol *sym)

+{

+	assert(sym->hide == 0);

+	sym->hide = 1;

+	DBG("SYM: hidding symbol %s %d", sym->name, sym->hide);

+}

+

+static void

+unhide(Symbol *sym)

+{

+	assert(sym->hide == 1);

+	DBG("SYM: unhidding symbol %s %d", sym->name, sym->hide);

+	sym->hide = 0;

+}

+

 int

-addinput(char *fname, Symbol *hide, char *buffer, int fail)

+addinput(char *fname, Symbol *sym, char *buffer, int fail)

 {

 	FILE *fp;

 	char *extp;

@@ -50,13 +66,14 @@

 	int infileln;

 	Input *newip, *curip = input;

-	if (hide) {

+	if (curip)

+		curip->lineno = lineno;

+

+	if (sym) {

 		/* this is a macro expansion */

 		fp = NULL;

-		if (hide->hide == UCHAR_MAX)

-			die("cc1: too many macro expansions");

-		DBG("SYM: hidding symbol %s %d\n", hide->name, hide->hide);

-		++hide->hide;

+		DBG("MACRO: %s expanded to '%s'", sym->name, buffer);

+		hide(sym);

 		flags = IMACRO;

 	} else  if (fname) {

 		/* a new file */

@@ -73,33 +90,31 @@

 			printf("%.*s.o: %s %s\n",

 			       infileln, infile, infile, fname);

 		}

+		lineno = 0;

 	} else {

 		/* reading from stdin */

 		fp = stdin;

 		fname = "<stdin>";

 		flags = ISTDIN;

+		lineno = 0;

 	}

-	newip = xmalloc(sizeof(*newip));

-

 	if (!buffer) {

 		buffer = xmalloc(INPUTSIZ);

 		buffer[0] = '\0';

 	}

-	if (curip)

-		curip->lineno = lineno;

-

+	newip = xmalloc(sizeof(*newip));

+	newip->next = curip;

+	newip->macro = sym;

+	newip->lineno = lineno;

 	newip->p = newip->begin = newip->line = buffer;

 	newip->filenam = NULL;

-	newip->lineno = 0;

-	newip->next = curip;

 	newip->fp = fp;

-	newip->hide = hide;

 	newip->flags = flags;

 	input = newip;

-	setloc(fname, (curip) ? curip->lineno : newip->lineno);

+	setloc(fname, lineno);

 	return 1;

 }

@@ -107,7 +122,6 @@

 delinput(void)

 {

 	Input *ip = input;

-	Symbol *hide = ip->hide;

 	switch (ip->flags & ITYPE) {

 	case IFILE:

@@ -115,18 +129,16 @@

 			die("cc1: %s: %s", ip->filenam, strerror(errno));

 		break;

 	case IMACRO:

-		assert(hide->hide == 1);

-		DBG("SYM: unhidding symbol %s %d\n", hide->name, hide->hide);

-		--hide->hide;

+		unhide(ip->macro);

 		break;

 	}

+

 	input = ip->next;

 	free(ip->filenam);

 	free(ip->line);

-	if (input) {

-		lineno = input->lineno;

-		strcpy(filenam, input->filenam);

-	}

+	free(ip);

+	if (input)

+		setloc(input->filenam, input->lineno);

 }

 static void