there's a buffer size problem that is very rarely hit by any normal
programs but appears when compiling some of the nuttier lunix code.

solution: if a line of code is longer than the default buffer size
(30k) then we realloc the buffer.

this isn't currently triggered by any plan9 code and will hopefully
never be.

for an example of what could happen in loonix-land see this gcc-parsed
code:

http://pages.cpsc.ucalgary.ca/~mirtchov/screenshots/ffmpeg.gif

andrey

Reference: /n/sources/patch/applied/cpp-buffer
Date: Sat Oct 16 06:20:32 CES 2004

--- /sys/src/cmd/cpp/cpp.c	Sat Oct 16 06:20:31 2004
+++ /sys/src/cmd/cpp/cpp.c	Sat Oct 16 06:20:31 2004
@@ -251,6 +251,16 @@
 }
 
 void *
+dorealloc(void *ptr, int size)
+{
+	void *p = realloc(ptr, size);
+
+	if (p==NULL)
+		error(FATAL, "Out of memory from realloc");
+	return p;
+}
+
+void *
 domalloc(int size)
 {
 	void *p = malloc(size);
--- /sys/src/cmd/cpp/cpp.h	Sat Oct 16 06:20:31 2004
+++ /sys/src/cmd/cpp/cpp.h	Sat Oct 16 06:20:31 2004
@@ -55,6 +55,7 @@
 	uchar	*inb;		/* input buffer */
 	uchar	*inp;		/* input pointer */
 	uchar	*inl;		/* end of input */
+	int 	ins;		/* input buffer size */
 	int	fd;		/* input source */
 	int	ifdepth;	/* conditional nesting in include */
 	struct	source *next;	/* stack for #include */
@@ -93,6 +94,7 @@
 void	unsetsource(void);
 void	puttokens(Tokenrow *);
 void	process(Tokenrow *);
+void	*dorealloc(void *, int);
 void	*domalloc(int);
 void	dofree(void *);
 void	error(enum errtype, char *, ...);
--- /sys/src/cmd/cpp/lex.c	Sat Oct 16 06:20:32 2004
+++ /sys/src/cmd/cpp/lex.c	Sat Oct 16 06:20:31 2004
@@ -319,7 +319,7 @@
 			s->inl = s->inb;
 			fillbuf(s);
 			ip = s->inp = s->inb;
-		} else if (ip >= s->inb+(3*INS/4)) {
+		} else if (ip >= s->inb+(3*s->ins/4)) {
 			memmove(s->inb, ip, 4+s->inl-ip);
 			s->inl = s->inb+(s->inl-ip);
 			ip = s->inp = s->inb;
@@ -445,7 +445,7 @@
 				state = COM2;
 				ip += runelen;
 				runelen = 1;
- 				if (ip >= s->inb+(7*INS/8)) { /* very long comment */
+ 				if (ip >= s->inb+(7*s->ins/8)) { /* very long comment */
 					memmove(tp->t, ip, 4+s->inl-ip);
 					s->inl -= ip-tp->t;
 					ip = tp->t+1;
@@ -537,9 +537,20 @@
 {
 	int n;
 
-	if ((char *)s->inl+INS/8 > (char *)s->inb+INS)
-		error(FATAL, "Input buffer overflow");
-	if (s->fd<0 || (n=read(s->fd, (char *)s->inl, INS/8)) <= 0)
+	while((char *)s->inl+s->ins/8 > (char *)s->inb+s->ins) {
+		uint l = s->inl - s->inb;
+		uint p = s->inp - s->inb;
+		if(l < 0) 
+			error(FATAL, "negative end of input!?");
+		if(p < 0)
+			error(FATAL, "negative input pointer!?");
+		/* double the buffer size and try again */
+		s->ins *= 2;
+		s->inb = dorealloc(s->inb, s->ins);
+		s->inl = s->inb + l;
+		s->inp = s->inb + p;
+	}
+	if (s->fd<0 || (n=read(s->fd, (char *)s->inl, s->ins/8)) <= 0)
 		n = 0;
 	if ((*s->inp&0xff) == EOB) /* sentinel character appears in input */
 		*s->inp = EOFC;
@@ -592,6 +603,8 @@
 		s->inp = s->inb;
 		len = 0;
 	}
+
+	s->ins = INS;	
 	s->inl = s->inp+len;
 	s->inl[0] = s->inl[1] = EOB;
 	return s;