Delete the mdoc_node.pending pointer and the function calculating

it, make_pending(), which was the most difficult function of the
whole mdoc(7) parser.  After almost five years of maintaining this
hellhole, i just noticed the pointer isn't needed after all.

Blocks are always rewound in the reverse order they were opened;
that even holds for broken blocks.  Consequently, it is sufficient
to just mark broken blogs with the flag MDOC_BROKEN and breaking
blocks with the flag MDOC_ENDED.  When rewinding, instead of iterating
the pending pointers, just iterate from each broken block to its
parents, rewinding all that are MDOC_ENDED and stopping after
processing the first ancestor that it not MDOC_BROKEN.  For ENDBODY
markers, use the mdoc_node.body pointer in place of the former
mdoc_node.pending.

This also fixes an assertion failure found by jsg@ with afl,
test case #467 (Bo Bl It Bd Bc It), where (surprise surprise)
the pending pointer got corrupted.

Improved functionality, minus one function, minus one struct field,
minus 50 lines of code.

1 files changed, 5 insertions, 39 deletions

diff --git a/mdoc_validate.c b/mdoc_validate.c
index 94e36d9f..21948506 100644
--- a/mdoc_validate.c
+++ b/mdoc_validate.c
@@ -325,7 +325,7 @@ mdoc_valid_post(struct mdoc *mdoc)
 	n = mdoc->last;
 	if (n->flags & MDOC_VALID)
 		return;
-	n->flags |= MDOC_VALID;
+	n->flags |= MDOC_VALID | MDOC_ENDED;
 
 	switch (n->type) {
 	case MDOC_TEXT:
@@ -416,24 +416,13 @@ pre_display(PRE_ARGS)
 static void
 pre_bl(PRE_ARGS)
 {
-	struct mdoc_node *np;
 	struct mdoc_argv *argv, *wa;
 	int		  i;
 	enum mdocargt	  mdoclt;
 	enum mdoc_list	  lt;
 
-	if (MDOC_BLOCK != n->type) {
-		if (ENDBODY_NOT != n->end) {
-			assert(n->pending);
-			np = n->pending->parent;
-		} else
-			np = n->parent;
-
-		assert(np);
-		assert(MDOC_BLOCK == np->type);
-		assert(MDOC_Bl == np->tok);
+	if (n->type != MDOC_BLOCK)
 		return;
-	}
 
 	/*
 	 * First figure out which kind of list to use: bind ourselves to
@@ -609,25 +598,14 @@ pre_bl(PRE_ARGS)
 static void
 pre_bd(PRE_ARGS)
 {
-	struct mdoc_node *np;
 	struct mdoc_argv *argv;
 	int		  i;
 	enum mdoc_disp	  dt;
 
 	pre_literal(mdoc, n);
 
-	if (MDOC_BLOCK != n->type) {
-		if (ENDBODY_NOT != n->end) {
-			assert(n->pending);
-			np = n->pending->parent;
-		} else
-			np = n->parent;
-
-		assert(np);
-		assert(MDOC_BLOCK == np->type);
-		assert(MDOC_Bd == np->tok);
+	if (n->type != MDOC_BLOCK)
 		return;
-	}
 
 	for (i = 0; n->args && i < (int)n->args->argc; i++) {
 		argv = n->args->argv + i;
@@ -797,22 +775,10 @@ post_bf(POST_ARGS)
 	 * element, which contains the goods.
 	 */
 
-	if (MDOC_HEAD != mdoc->last->type) {
-		if (ENDBODY_NOT != mdoc->last->end) {
-			assert(mdoc->last->pending);
-			np = mdoc->last->pending->parent->head;
-		} else if (MDOC_BLOCK != mdoc->last->type) {
-			np = mdoc->last->parent->head;
-		} else
-			np = mdoc->last->head;
-
-		assert(np);
-		assert(MDOC_HEAD == np->type);
-		assert(MDOC_Bf == np->tok);
+	np = mdoc->last;
+	if (MDOC_HEAD != np->type)
 		return;
-	}
 
-	np = mdoc->last;
 	assert(MDOC_BLOCK == np->parent->type);
 	assert(MDOC_Bf == np->parent->tok);