From 3e043306f1594f7528788a1c593995b391fc7a5a Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Thu, 25 Oct 2001 19:28:43 +0000
Subject: Enforce proper ordering of heading levels: specifically, ensure the
 user doesn't skip a heading level (\H before any \C or \A, or \S straight
 after \C with no intervening \H). The precise criterion is that when creating
 section a.b.c.d, sections a.b.c, a.b and a should already exist. This ensures
 the section tree really is a properly formed tree with no missing nodes.

[originally from svn r1329]
---
 buttress.h         |  3 ++-
 contents.c         | 11 ++++++++++-
 error.c            |  5 +++++
 inputs/errors2.but |  5 +++++
 keywords.c         | 16 +++++++++++++++-
 main.c             |  2 ++
 6 files changed, 39 insertions(+), 3 deletions(-)
 create mode 100644 inputs/errors2.but

diff --git a/buttress.h b/buttress.h
index b07cf0a..8f8961a 100644
--- a/buttress.h
+++ b/buttress.h
@@ -199,6 +199,7 @@ enum {
     err_nosuchidxtag,		       /* \IM on unknown index tag (warning) */
     err_cantopenw,		       /* can't open output file for write */
     err_macroexists,		       /* this macro already exists */
+    err_sectjump,		       /* jump a heading level, eg \C -> \S */
     err_whatever                       /* random error of another type */
 };
 
@@ -374,7 +375,7 @@ void index_debug(index *);
  */
 numberstate *number_init(void);
 void number_cfg(numberstate *, paragraph *);
-word *number_mktext(numberstate *, int, int, int, word **);
+word *number_mktext(numberstate *, int, int, int, word **, filepos);
 void number_free(numberstate *);
 
 /*
diff --git a/contents.c b/contents.c
index fee45d9..7688d75 100644
--- a/contents.c
+++ b/contents.c
@@ -13,6 +13,7 @@ struct numberstate_Tag {
     int appendixnum;
     int ischapter;
     int *sectionlevels;
+    int oklevel;
     int maxsectlevel;
     int listitem;
     wchar_t *chaptertext;	       /* the word for a chapter */
@@ -25,6 +26,7 @@ numberstate *number_init(void) {
     ret->chapternum = 0;
     ret->appendixnum = -1;
     ret->ischapter = 1;
+    ret->oklevel = -1;		       /* not even in a chapter yet */
     ret->maxsectlevel = 32;
     ret->sectionlevels = mknewa(int, ret->maxsectlevel);
     ret->listitem = -1;
@@ -114,7 +116,7 @@ void number_cfg(numberstate *state, paragraph *source) {
 }
 
 word *number_mktext(numberstate *state, int para, int aux, int prev,
-		    word **auxret) {
+		    word **auxret, filepos fpos) {
     word *ret = NULL;
     word **ret2 = &ret;
     word **pret = &ret;
@@ -130,10 +132,16 @@ word *number_mktext(numberstate *state, int para, int aux, int prev,
 	ret2 = pret;
 	donumber(&pret, state->chapternum);
 	state->ischapter = 1;
+	state->oklevel = 0;
 	break;
       case para_Heading:
       case para_Subsect:
 	level = (para == para_Heading ? 0 : aux);
+	if (level > state->oklevel) {
+	    error(err_sectjump, &fpos);
+	    return NULL;
+	}
+	state->oklevel = level+1;
 	if (state->maxsectlevel <= level) {
 	    state->maxsectlevel = level + 32;
 	    state->sectionlevels = resize(state->sectionlevels,
@@ -165,6 +173,7 @@ word *number_mktext(numberstate *state, int para, int aux, int prev,
 	ret2 = pret;
 	doanumber(&pret, state->appendixnum);
 	state->ischapter = 0;
+	state->oklevel = 0;
 	break;
       case para_NumberedList:
 	ret2 = pret;
diff --git a/error.c b/error.c
index b4a3898..c81aa8c 100644
--- a/error.c
+++ b/error.c
@@ -162,6 +162,11 @@ static void do_error(int code, va_list ap) {
 	sprintf(error, "macro `%.200s' already defined", sp);
 	flags = FILEPOS;
 	break;
+      case err_sectjump:
+	fpos = *va_arg(ap, filepos *);
+	sprintf(error, "expected higher heading levels before this one");
+	flags = FILEPOS;
+	break;
       case err_whatever:
 	sp = va_arg(ap, char *);
         vsprintf(error, sp, ap);
diff --git a/inputs/errors2.but b/inputs/errors2.but
new file mode 100644
index 0000000..b1a3303
--- /dev/null
+++ b/inputs/errors2.but
@@ -0,0 +1,5 @@
+\H{outofplace} Heading out of place.
+
+\C{chap} Chapter is fine
+
+\S{subsect} Subsection should have heading before it.
diff --git a/keywords.c b/keywords.c
index d0d0b4d..7dd35b1 100644
--- a/keywords.c
+++ b/keywords.c
@@ -86,6 +86,7 @@ keyword *kw_lookup(keywordlist *kl, wchar_t *str) {
  * finish).
  */
 keywordlist *get_keywords(paragraph *source) {
+    int errors = FALSE;
     keywordlist *kl = mknew(keywordlist);
     numberstate *n = number_init();
     int prevpara = para_NotParaType;
@@ -102,7 +103,15 @@ keywordlist *get_keywords(paragraph *source) {
 	 * Number the chapter / section / list-item / whatever.
 	 */
 	source->kwtext = number_mktext(n, source->type, source->aux,
-				       prevpara, &source->kwtext2);
+				       prevpara, &source->kwtext2,
+				       source->fpos);
+	if (!source->kwtext) {
+	    /* There was an error collecting the section numbers.
+	     * number_mktext has reported it; we record it and bail
+	     * out at the end. */
+	    errors = TRUE;
+	    continue;
+	}
 	prevpara = source->type;
 
 	if (source->keyword && *source->keyword) {
@@ -128,6 +137,11 @@ keywordlist *get_keywords(paragraph *source) {
 
     number_free(n);
 
+    if (errors) {
+	free_keywords(kl);
+	return NULL;
+    }
+
     heap_sort(kl);
 
     return kl;
diff --git a/main.c b/main.c
index 079aba8..b7be46f 100644
--- a/main.c
+++ b/main.c
@@ -197,6 +197,8 @@ int main(int argc, char **argv) {
 	sfree(infiles);
 
 	keywords = get_keywords(sourceform);
+	if (!keywords)
+	    exit(EXIT_FAILURE);
 	gen_citations(sourceform, keywords);
 	subst_keywords(sourceform, keywords);
 
-- 
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