Chain error messages in more files.

23 files changed, 198 insertions, 181 deletions

diff --git a/mupdf/pdf_annot.c b/mupdf/pdf_annot.c
index a2839f6e..df40091b 100644
--- a/mupdf/pdf_annot.c
+++ b/mupdf/pdf_annot.c
@@ -101,7 +101,7 @@ pdf_loadlink(pdf_link **linkp, pdf_xref *xref, fz_obj *dict)
 	{
 		error = pdf_resolve(&obj, xref);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot resolve /Dest");
 		dest = resolvedest(xref, obj);
 		pdf_logpage("dest %d %d R\n", fz_tonum(dest), fz_togen(dest));
 		fz_dropobj(obj);
@@ -112,7 +112,7 @@ pdf_loadlink(pdf_link **linkp, pdf_xref *xref, fz_obj *dict)
 	{
 		error = pdf_resolve(&action, xref);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot resolve /A");
 
 		obj = fz_dictgets(action, "S");
 		if (!strcmp(fz_toname(obj), "GoTo"))
@@ -137,7 +137,7 @@ pdf_loadlink(pdf_link **linkp, pdf_xref *xref, fz_obj *dict)
 	{
 		error = pdf_newlink(&link, bbox, dest);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot create link");
 		*linkp = link;
 	}
 
@@ -164,7 +164,10 @@ pdf_loadannots(pdf_comment **cp, pdf_link **lp, pdf_xref *xref, fz_obj *annots)
 		obj = fz_arrayget(annots, i);
 		error = pdf_resolve(&obj, xref);
 		if (error)
-			goto cleanup;
+		{
+			pdf_droplink(link);
+			return fz_rethrow(error, "cannot resolve annotation");
+		}
 
 		subtype = fz_dictgets(obj, "Subtype");
 		if (!strcmp(fz_toname(subtype), "Link"))
@@ -174,7 +177,10 @@ pdf_loadannots(pdf_comment **cp, pdf_link **lp, pdf_xref *xref, fz_obj *annots)
 			error = pdf_loadlink(&temp, xref, obj);
 			fz_dropobj(obj);
 			if (error)
-				goto cleanup;
+			{
+				pdf_droplink(link);
+				return fz_rethrow(error, "cannot load annotation link");
+			}
 
 			if (temp)
 			{
@@ -187,7 +193,10 @@ pdf_loadannots(pdf_comment **cp, pdf_link **lp, pdf_xref *xref, fz_obj *annots)
 			error = loadcomment(&comment, xref, obj);
 			fz_dropobj(obj);
 			if (error)
-				goto cleanup;
+			{
+				pdf_droplink(link);
+				return fz_rethrow(error, "cannot load annotation comment");
+			}
 		}
 	}
 
@@ -196,9 +205,5 @@ pdf_loadannots(pdf_comment **cp, pdf_link **lp, pdf_xref *xref, fz_obj *annots)
 	*cp = comment;
 	*lp = link;
 	return nil;
-
-cleanup:
-	pdf_droplink(link);
-	return error;
 }
 
diff --git a/mupdf/pdf_build.c b/mupdf/pdf_build.c
index 87748d95..e62ebd0d 100644
--- a/mupdf/pdf_build.c
+++ b/mupdf/pdf_build.c
@@ -673,7 +673,7 @@ pdf_showpath(pdf_csi *csi,
 	{
 		error = fz_clonepathnode(&clip, csi->path);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot copy path node for clip mask");
 	}
 
 	if (dofill && dostroke)
diff --git a/mupdf/pdf_cmap.c b/mupdf/pdf_cmap.c
index 9031aeb6..20337eed 100644
--- a/mupdf/pdf_cmap.c
+++ b/mupdf/pdf_cmap.c
@@ -597,13 +597,13 @@ static int codefromstring(unsigned char *buf, int len)
 	return a;
 }
 
-static fz_error *mylex(int *token, fz_stream *file, char *buf, int n, int *sl)
+static fz_error *lexcmap(int *token, fz_stream *file, char *buf, int n, int *sl)
 {
 	fz_error *error;
 	error = pdf_lex(token, file, buf, n, sl);
 	if (!error && *token == PDF_TKEYWORD)
 		*token = tokenfromkeyword(buf);
-	return error;
+	return fz_rethrow(error, "cannot parse cmap token");
 }
 
 static fz_error *parsecmapname(pdf_cmap *cmap, fz_stream *file)
@@ -613,7 +613,7 @@ static fz_error *parsecmapname(pdf_cmap *cmap, fz_stream *file)
 	int token;
 	int len;
 
-	error = mylex(&token, file, buf, sizeof buf, &len);
+	error = lexcmap(&token, file, buf, sizeof buf, &len);
 	if (error)
 		return fz_rethrow(error, "syntaxerror in cmap");
 
@@ -633,7 +633,7 @@ static fz_error *parsewmode(pdf_cmap *cmap, fz_stream *file)
 	int token;
 	int len;
 
-	error = mylex(&token, file, buf, sizeof buf, &len);
+	error = lexcmap(&token, file, buf, sizeof buf, &len);
 	if (error)
 		return fz_rethrow(error, "syntaxerror in cmap");
 
@@ -656,7 +656,7 @@ static fz_error *parsecodespacerange(pdf_cmap *cmap, fz_stream *file)
 
 	while (1)
 	{
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 
@@ -666,7 +666,7 @@ static fz_error *parsecodespacerange(pdf_cmap *cmap, fz_stream *file)
 		else if (token == PDF_TSTRING)
 		{
 			lo = codefromstring(buf, len);
-			error = mylex(&token, file, buf, sizeof buf, &len);
+			error = lexcmap(&token, file, buf, sizeof buf, &len);
 			if (error)
 				return fz_rethrow(error, "syntaxerror in cmap");
 			if (token == PDF_TSTRING)
@@ -695,7 +695,7 @@ static fz_error *parsecidrange(pdf_cmap *cmap, fz_stream *file)
 
 	while (1)
 	{
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 
@@ -707,7 +707,7 @@ static fz_error *parsecidrange(pdf_cmap *cmap, fz_stream *file)
 
 		lo = codefromstring(buf, len);
 
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 		if (token != PDF_TSTRING)
@@ -715,7 +715,7 @@ static fz_error *parsecidrange(pdf_cmap *cmap, fz_stream *file)
 
 		hi = codefromstring(buf, len);
 
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 		if (token != PDF_TINT)
@@ -739,7 +739,7 @@ static fz_error *parsecidchar(pdf_cmap *cmap, fz_stream *file)
 
 	while (1)
 	{
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 
@@ -751,7 +751,7 @@ static fz_error *parsecidchar(pdf_cmap *cmap, fz_stream *file)
 
 		src = codefromstring(buf, len);
 
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 		if (token != PDF_TINT)
@@ -776,7 +776,7 @@ static fz_error *parsebfrangearray(pdf_cmap *cmap, fz_stream *file, int lo, int
 
 	while (1)
 	{
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 
@@ -811,7 +811,7 @@ static fz_error *parsebfrange(pdf_cmap *cmap, fz_stream *file)
 
 	while (1)
 	{
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 
@@ -823,7 +823,7 @@ static fz_error *parsebfrange(pdf_cmap *cmap, fz_stream *file)
 
 		lo = codefromstring(buf, len);
 
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 		if (token != PDF_TSTRING)
@@ -831,7 +831,7 @@ static fz_error *parsebfrange(pdf_cmap *cmap, fz_stream *file)
 
 		hi = codefromstring(buf, len);
 
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 
@@ -892,7 +892,7 @@ static fz_error *parsebfchar(pdf_cmap *cmap, fz_stream *file)
 
 	while (1)
 	{
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 
@@ -904,7 +904,7 @@ static fz_error *parsebfchar(pdf_cmap *cmap, fz_stream *file)
 
 		src = codefromstring(buf, len);
 
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 			return fz_rethrow(error, "syntaxerror in cmap");
 		/* Note: does not handle /dstName */
@@ -941,7 +941,7 @@ pdf_parsecmap(pdf_cmap **cmapp, fz_stream *file)
 
 	while (1)
 	{
-		error = mylex(&token, file, buf, sizeof buf, &len);
+		error = lexcmap(&token, file, buf, sizeof buf, &len);
 		if (error)
 		{
 			error = fz_rethrow(error, "syntaxerror in cmap");
@@ -1045,7 +1045,7 @@ pdf_parsecmap(pdf_cmap **cmapp, fz_stream *file)
 
 cleanup:
 	pdf_dropcmap(cmap);
-	return error;
+	return error; /* already rethrown */
 }
 
 /*
@@ -1141,7 +1141,7 @@ cleanup:
 	if (cmap)
 		pdf_dropcmap(cmap);
 	fz_dropobj(stmobj);
-	return error;
+	return error; /* already rethrown */
 }
 
 /*
@@ -1211,7 +1211,7 @@ cleanup:
 		pdf_dropcmap(cmap);
 	if (file)
 		fz_dropstream(file);
-	return error;
+	return error; /* already rethrown */
 }
 
 /*
diff --git a/mupdf/pdf_colorspace1.c b/mupdf/pdf_colorspace1.c
index 7c79f79a..9d7c740b 100644
--- a/mupdf/pdf_colorspace1.c
+++ b/mupdf/pdf_colorspace1.c
@@ -233,11 +233,11 @@ loadcalgray(fz_colorspace **csp, pdf_xref *xref, fz_obj *dict)
 
 	error = pdf_resolve(&dict, xref);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot find colorspace");
 
 	cs = fz_malloc(sizeof(struct calgray));
 	if (!cs)
-		return fz_outofmem;
+		return fz_throw("outofmem: gray colorspace struct");
 
 	pdf_logrsrc("load CalGray\n");
 
@@ -289,11 +289,11 @@ loadcalrgb(fz_colorspace **csp, pdf_xref *xref, fz_obj *dict)
 
 	error = pdf_resolve(&dict, xref);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot find colorspace");
 
 	cs = fz_malloc(sizeof(struct calrgb));
 	if (!cs)
-		return fz_outofmem;
+		return fz_throw("outofmem: RGB colorspace struct");
 
 	pdf_logrsrc("load CalRGB\n");
 
@@ -363,11 +363,11 @@ loadlab(fz_colorspace **csp, pdf_xref *xref, fz_obj *dict)
 
 	error = pdf_resolve(&dict, xref);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot find colorspace");
 
 	cs = fz_malloc(sizeof(struct cielab));
 	if (!cs)
-		return fz_outofmem;
+		return fz_throw("outofmem: L*a*b colorspace struct");
 
 	pdf_logrsrc("load Lab\n");
 
@@ -434,7 +434,7 @@ loadiccbased(fz_colorspace **csp, pdf_xref *xref, fz_obj *ref)
 
 	error = pdf_loadindirect(&dict, xref, ref);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot find colorspace");
 
 	n = fz_toint(fz_dictgets(dict, "N"));
 
@@ -512,17 +512,18 @@ loadseparation(fz_colorspace **csp, pdf_xref *xref, fz_obj *array)
 
 	error = pdf_resolve(&baseobj, xref);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot find colorspace");
+
 	error = pdf_loadcolorspace(&base, xref, baseobj);
 	fz_dropobj(baseobj);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot load base colorspace");
 
 	error = pdf_loadfunction(&tint, xref, tintobj);
 	if (error)
 	{
 		fz_dropcolorspace(base);
-		return error;
+		return fz_rethrow(error, "cannot load tint function");
 	}
 
 	cs = fz_malloc(sizeof(struct separation));
@@ -530,7 +531,7 @@ loadseparation(fz_colorspace **csp, pdf_xref *xref, fz_obj *array)
 	{
 		pdf_dropfunction(tint);
 		fz_dropcolorspace(base);
-		return fz_outofmem;
+		return fz_throw("outofmem: separation colorspace struct");
 	}
 
 	initcs((fz_colorspace*)cs,
@@ -588,11 +589,12 @@ loadindexed(fz_colorspace **csp, pdf_xref *xref, fz_obj *array)
 
 	error = pdf_resolve(&baseobj, xref);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot find colorspace");
+
 	error = pdf_loadcolorspace(&base, xref, baseobj);
 	fz_dropobj(baseobj);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot load base colorspace");
 
 	pdf_logrsrc("base %s\n", base->name);
 
@@ -600,7 +602,7 @@ loadindexed(fz_colorspace **csp, pdf_xref *xref, fz_obj *array)
 	if (!cs)
 	{
 		fz_dropcolorspace(base);
-		return fz_outofmem;
+		return fz_throw("outofmem: indexed colorspace struct");
 	}
 
 	initcs((fz_colorspace*)cs, "Indexed", 1, nil, nil, dropindexed);
@@ -614,7 +616,7 @@ loadindexed(fz_colorspace **csp, pdf_xref *xref, fz_obj *array)
 	if (!cs->lookup)
 	{
 		fz_dropcolorspace((fz_colorspace*)cs);
-		return fz_outofmem;
+		return fz_throw("outofmem: indexed colorspace lookup table (%d entries)", n);
 	}
 
 	if (fz_isstring(lookup) && fz_tostrlen(lookup) == n)
@@ -640,7 +642,7 @@ loadindexed(fz_colorspace **csp, pdf_xref *xref, fz_obj *array)
 		if (error)
 		{
 			fz_dropcolorspace((fz_colorspace*)cs);
-			return error;
+			return fz_rethrow(error, "cannot load colorpsace lookup table");
 		}
 
 		for (i = 0; i < n && i < (buf->wp - buf->rp); i++)
@@ -737,10 +739,12 @@ pdf_loadcolorspace(fz_colorspace **csp, pdf_xref *xref, fz_obj *obj)
 
 				error = pdf_resolve(&obj, xref);
 				if (error)
-					return error;
+					return fz_rethrow(error, "cannot find pattern");
+
 				error = pdf_loadcolorspace(csp, xref, obj);
 				fz_dropobj(obj);
-				return error;
+				if (error)
+					return fz_rethrow(error, "cannot load pattern");
 			}
 
 			else
diff --git a/mupdf/pdf_doctor.c b/mupdf/pdf_doctor.c
index deb33af3..f9e56957 100644
--- a/mupdf/pdf_doctor.c
+++ b/mupdf/pdf_doctor.c
@@ -21,7 +21,7 @@ sweepobj(pdf_xref *xref, fz_obj *obj)
 		{
 			error = sweepobj(xref, fz_dictgetval(obj, i));
 			if (error)
-				return error;
+				return error; /* too deeply nested for rethrow */
 		}
 	}
 
@@ -31,7 +31,7 @@ sweepobj(pdf_xref *xref, fz_obj *obj)
 		{
 			error = sweepobj(xref, fz_arrayget(obj, i));
 			if (error)
-				return error;
+				return error; /* too deeply nested for rethrow */
 		}
 	}
 
@@ -66,7 +66,7 @@ sweepref(pdf_xref *xref, fz_obj *ref)
 	if (error)
 	{
 		fz_dropobj(obj);
-		return error;
+		return error; /* too deeply nested for rethrow */
 	}
 
 	fz_dropobj(obj);
diff --git a/mupdf/pdf_font.c b/mupdf/pdf_font.c
index a2386fed..6e5fd083 100644
--- a/mupdf/pdf_font.c
+++ b/mupdf/pdf_font.c
@@ -577,7 +577,7 @@ cleanup:
 	if (widths)
 		fz_dropobj(widths);
 	fz_dropfont((fz_font*)font);
-	return error;
+	return fz_rethrow(error, "cannot load simple font");
 }
 
 /*
@@ -614,7 +614,7 @@ loadcidfont(pdf_font **fontp, pdf_xref *xref, fz_obj *dict, fz_obj *ref, fz_obj
 
 		error = pdf_resolve(&cidinfo, xref);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot find CIDSystemInfo");
 
 		obj = fz_dictgets(cidinfo, "Registry");
 		tmplen = MIN(sizeof tmpstr - 1, fz_tostrlen(obj));
@@ -759,7 +759,7 @@ loadcidfont(pdf_font **fontp, pdf_xref *xref, fz_obj *dict, fz_obj *ref, fz_obj
 				error = nil;
 
 			if (error)
-				return error;
+				return fz_rethrow(error, "cannot load system cmap %s", collection);
 		}
 	}
 
@@ -891,7 +891,7 @@ cleanup:
 	if (widths)
 		fz_dropobj(widths);
 	fz_dropfont((fz_font*)font);
-	return error;
+	return fz_rethrow(error, "cannot load cid font");
 }
 
 static fz_error *
@@ -907,12 +907,15 @@ loadtype0(pdf_font **fontp, pdf_xref *xref, fz_obj *dict, fz_obj *ref)
 	dfonts = fz_dictgets(dict, "DescendantFonts");
 	error = pdf_resolve(&dfonts, xref);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot find DescendantFonts");
 
 	dfont = fz_arrayget(dfonts, 0);
 	error = pdf_resolve(&dfont, xref);
 	if (error)
-		return fz_dropobj(dfonts), error;
+	{
+		fz_dropobj(dfonts);
+		return fz_rethrow(error, "cannot find descendant font");
+	}
 
 	subtype = fz_dictgets(dfont, "Subtype");
 	encoding = fz_dictgets(dict, "Encoding");
@@ -929,7 +932,7 @@ loadtype0(pdf_font **fontp, pdf_xref *xref, fz_obj *dict, fz_obj *ref)
 	fz_dropobj(dfonts);
 
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot load descendant font");
 
 	return nil;
 }
@@ -948,7 +951,7 @@ pdf_loadfontdescriptor(pdf_font *font, pdf_xref *xref, fz_obj *desc, char *colle
 
 	error = pdf_resolve(&desc, xref);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot find font descriptor");
 
 	pdf_logfont("load fontdescriptor {\n");
 
@@ -1000,7 +1003,7 @@ pdf_loadfontdescriptor(pdf_font *font, pdf_xref *xref, fz_obj *desc, char *colle
 
 cleanup:
 	fz_dropobj(desc);
-	return error;
+	return fz_rethrow(error, "cannot load font descriptor");
 }
 
 fz_error *
@@ -1025,14 +1028,14 @@ pdf_loadfont(pdf_font **fontp, pdf_xref *xref, fz_obj *dict, fz_obj *ref)
 	else if (!strcmp(subtype, "Type3"))
 		error = pdf_loadtype3font(fontp, xref, dict, ref);
 	else
-		error = fz_throw("unimplemented: %s fonts", subtype);
+		return fz_throw("cannot recognize font format %s", subtype);
 
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot load font");
 
 	error = pdf_storeitem(xref->store, PDF_KFONT, ref, *fontp);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot store font resource");
 
 	return nil;
 }
diff --git a/mupdf/pdf_interpret.c b/mupdf/pdf_interpret.c
index 52619720..700b5c8f 100644
--- a/mupdf/pdf_interpret.c
+++ b/mupdf/pdf_interpret.c
@@ -165,7 +165,7 @@ runxobject(pdf_csi *csi, pdf_xref *xref, pdf_xobject *xobj, int istransparency)
 	/* gsave */
 	error = gsave(csi);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot push graphics state");
 
 	/* reset alpha to 1.0 when starting a new Transparency group */
 	if (istransparency) {
@@ -205,7 +205,7 @@ runxobject(pdf_csi *csi, pdf_xref *xref, pdf_xobject *xobj, int istransparency)
 	/* grestore */
 	error = grestore(csi);
 	if (error)
-		return fz_rethrow(error, "cannot grestore");
+		return fz_rethrow(error, "cannot pop graphics state");
 
 	return fz_okay;
 }
diff --git a/mupdf/pdf_nametree.c b/mupdf/pdf_nametree.c
index 706c0e50..49396c50 100644
--- a/mupdf/pdf_nametree.c
+++ b/mupdf/pdf_nametree.c
@@ -13,14 +13,17 @@ loadnametreenode(fz_obj *tree, pdf_xref *xref, fz_obj *node)
 
 	error = pdf_resolve(&node, xref);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot resolve name tree");
 
 	names = fz_dictgets(node, "Names");
 	if (names)
 	{
 		error = pdf_resolve(&names, xref);
 		if (error)
-			goto cleanup;
+		{
+			fz_dropobj(node);
+			return fz_rethrow(error, "cannot resolve /Names");
+		}
 
 		len = fz_arraylen(names) / 2;
 
@@ -32,7 +35,8 @@ loadnametreenode(fz_obj *tree, pdf_xref *xref, fz_obj *node)
 			if (error)
 			{
 				fz_dropobj(names);
-				goto cleanup;
+				fz_dropobj(node);
+				return fz_rethrow(error, "cannot insert name tree entry");
 			}
 		}
 
@@ -44,7 +48,10 @@ loadnametreenode(fz_obj *tree, pdf_xref *xref, fz_obj *node)
 	{
 		error = pdf_resolve(&kids, xref);
 		if (error)
-			goto cleanup;
+		{
+			fz_dropobj(node);
+			return fz_rethrow(error, "cannot resolve /Kids");
+		}
 
 		len = fz_arraylen(kids);
 		for (i = 0; i < len; ++i)
@@ -53,7 +60,8 @@ loadnametreenode(fz_obj *tree, pdf_xref *xref, fz_obj *node)
 			if (error)
 			{
 				fz_dropobj(kids);
-				goto cleanup;
+				fz_dropobj(node);
+				return fz_rethrow(error, "cannot load name tree node");
 			}
 		}
 
@@ -62,10 +70,6 @@ loadnametreenode(fz_obj *tree, pdf_xref *xref, fz_obj *node)
 
 	fz_dropobj(node);
 	return nil;
-
-cleanup:
-	fz_dropobj(node);
-	return error;
 }
 
 fz_error *
@@ -76,13 +80,13 @@ pdf_loadnametree(fz_obj **dictp, pdf_xref *xref, fz_obj *root)
 
 	error = fz_newdict(&tree, 128);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot create name tree dictionary");
 
 	error = loadnametreenode(tree, xref, root);
 	if (error)
 	{
 		fz_dropobj(tree);
-		return error;
+		return fz_rethrow(error, "cannot load name tree");
 	}
 
 	fz_sortdict(tree);
@@ -104,7 +108,7 @@ pdf_loadnametrees(pdf_xref *xref)
 	{
 		error = pdf_resolve(&dests, xref);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot resolve /Dests");
 		xref->dests = dests;
 		return nil;
 	}
@@ -115,7 +119,7 @@ pdf_loadnametrees(pdf_xref *xref)
 	{
 		error = pdf_resolve(&names, xref);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot resolve /Names");
 		dests = fz_dictgets(names, "Dests");
 		if (dests)
 		{
@@ -123,7 +127,7 @@ pdf_loadnametrees(pdf_xref *xref)
 			if (error)
 			{
 				fz_dropobj(names);
-				return error;
+				return fz_rethrow(error, "cannot load name tree");
 			}
 		}
 		fz_dropobj(names);
diff --git a/mupdf/pdf_open.c b/mupdf/pdf_open.c
index e9facef4..9b7dfeb5 100644
--- a/mupdf/pdf_open.c
+++ b/mupdf/pdf_open.c
@@ -292,8 +292,8 @@ readnewxref(fz_obj **trailerp, pdf_xref *xref, char *buf, int cap)
 
 	if (oid < 0 || oid >= xref->len)
 	{
-		error = fz_throw("object id out of range");
-		goto cleanup;
+		fz_dropobj(trailer);
+		return fz_throw("object id out of range");
 	}
 
 	xref->table[oid].type = 'n';
@@ -304,15 +304,15 @@ readnewxref(fz_obj **trailerp, pdf_xref *xref, char *buf, int cap)
 	obj = fz_dictgets(trailer, "Size");
 	if (!obj)
 	{
-		error = fz_throw("xref stream missing Size entry");
-		goto cleanup;
+		fz_dropobj(trailer);
+		return fz_throw("xref stream missing Size entry");
 	}
 	size = fz_toint(obj);
 
 	obj = fz_dictgets(trailer, "W");
 	if (!obj) {
-		error = fz_throw("xref stream missing W entry");
-		goto cleanup;
+		fz_dropobj(trailer);
+		return fz_throw("xref stream missing W entry");
 	}
 	w0 = fz_toint(fz_arrayget(obj, 0));
 	w1 = fz_toint(fz_arrayget(obj, 1));
@@ -329,15 +329,15 @@ readnewxref(fz_obj **trailerp, pdf_xref *xref, char *buf, int cap)
 	}
 
 	if (i0 < 0 || i1 > xref->len) {
-		error = fz_throw("xref stream has too many entries");
-		goto cleanup;
+		fz_dropobj(trailer);
+		return fz_throw("xref stream has too many entries");
 	}
 
 	error = pdf_openstream(&stm, xref, oid, gen);
 	if (error)
 	{
-		error = fz_rethrow(error, "cannot open compressed xref stream");
-		goto cleanup;
+		fz_dropobj(trailer);
+		return fz_rethrow(error, "cannot open compressed xref stream");
 	}
 
 	for (i = i0; i < i0 + i1; i++)
@@ -348,13 +348,12 @@ readnewxref(fz_obj **trailerp, pdf_xref *xref, char *buf, int cap)
 
 		if (fz_peekbyte(stm) == EOF)
 		{
+			fz_dropstream(stm);
+			fz_dropobj(trailer);
 			error = fz_readerror(stm);
 			if (error)
-				error = fz_rethrow(error, "truncated xref stream");
-			else
-				error = fz_throw("truncated xref stream");
-			fz_dropstream(stm);
-			goto cleanup;
+				return fz_rethrow(error, "truncated xref stream");
+			return fz_throw("truncated xref stream");
 		}
 
 		for (n = 0; n < w0; n++)
@@ -367,9 +366,9 @@ readnewxref(fz_obj **trailerp, pdf_xref *xref, char *buf, int cap)
 		error = fz_readerror(stm);
 		if (error)
 		{
-			error = fz_rethrow(error, "truncated xref stream");
 			fz_dropstream(stm);
-			goto cleanup;
+			fz_dropobj(trailer);
+			return fz_rethrow(error, "truncated xref stream");
 		}
 
 		if (!xref->table[i].type)
@@ -386,10 +385,6 @@ readnewxref(fz_obj **trailerp, pdf_xref *xref, char *buf, int cap)
 	*trailerp = trailer;
 
 	return nil;
-
-cleanup:
-	fz_dropobj(trailer);
-	return error;
 }
 
 static fz_error *
@@ -447,8 +442,8 @@ readxrefsections(pdf_xref *xref, int ofs, char *buf, int cap)
 		error = readxrefsections(xref, fz_toint(xrefstm), buf, cap);
 		if (error)
 		{
-			error = fz_rethrow(error, "cannot read /XrefStm xref section");
-			goto cleanup;
+			fz_dropobj(trailer);
+			return fz_rethrow(error, "cannot read /XrefStm xref section");
 		}
 	}
 
@@ -459,17 +454,13 @@ readxrefsections(pdf_xref *xref, int ofs, char *buf, int cap)
 		error = readxrefsections(xref, fz_toint(prev), buf, cap);
 		if (error)
 		{
-			error = fz_rethrow(error, "cannot read /Prev xref section");
-			goto cleanup;
+			fz_dropobj(trailer);
+			return fz_rethrow(error, "cannot read /Prev xref section");
 		}
 	}
 
 	fz_dropobj(trailer);
 	return nil;
-
-cleanup:
-	fz_dropobj(trailer);
-	return error;
 }
 
 /*
@@ -584,7 +575,7 @@ cleanupoid:
 	fz_free(oidbuf);
 cleanupobj:
 	fz_dropobj(objstm);
-	return error;
+	return error; /* already rethrown */
 }
 
 /*
diff --git a/mupdf/pdf_outline.c b/mupdf/pdf_outline.c
index c41d96f5..7bd47e51 100644
--- a/mupdf/pdf_outline.c
+++ b/mupdf/pdf_outline.c
@@ -21,7 +21,7 @@ loadoutline(pdf_outline **nodep, pdf_xref *xref, fz_obj *dict)
 	{
 		error = pdf_toutf8(&node->title, obj);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot convert Title to UTF-8");
 		pdf_logpage("title %s\n", node->title);
 	}
 
@@ -29,7 +29,7 @@ loadoutline(pdf_outline **nodep, pdf_xref *xref, fz_obj *dict)
 	{
 		error = pdf_loadlink(&node->link, xref, dict);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot load link");
 	}
 
 	obj = fz_dictgets(dict, "First");
@@ -37,11 +37,11 @@ loadoutline(pdf_outline **nodep, pdf_xref *xref, fz_obj *dict)
 	{
 		error = pdf_resolve(&obj, xref);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot resolve /First");
 		error = loadoutline(&node->child, xref, obj);
 		fz_dropobj(obj);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot load outline");
 	}
 
 	pdf_logpage("}\n");
@@ -51,11 +51,11 @@ loadoutline(pdf_outline **nodep, pdf_xref *xref, fz_obj *dict)
 	{
 		error = pdf_resolve(&obj, xref);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot resolve /Next");
 		error = loadoutline(&node->next, xref, obj);
 		fz_dropobj(obj);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot load outline");
 	}
 
 	*nodep = node;
@@ -79,7 +79,7 @@ pdf_loadoutline(pdf_outline **nodep, pdf_xref *xref)
 	{
 		error = pdf_resolve(&obj, xref);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot resolve /Outlines");
 
 		first = fz_dictgets(obj, "First");
 		if (first)
@@ -87,11 +87,11 @@ pdf_loadoutline(pdf_outline **nodep, pdf_xref *xref)
 			error = pdf_resolve(&first, xref);
 			fz_dropobj(obj);
 			if (error)
-				return error;
+				return fz_rethrow(error, "cannot resolve /First");
 			error = loadoutline(&node, xref, first);
 			fz_dropobj(first);
 			if (error)
-				return error;
+				return fz_rethrow(error, "cannot load outline");
 		}
 		else
 			fz_dropobj(obj);
diff --git a/mupdf/pdf_page.c b/mupdf/pdf_page.c
index f509737b..1d9f9879 100644
--- a/mupdf/pdf_page.c
+++ b/mupdf/pdf_page.c
@@ -103,7 +103,7 @@ cleanupstm:
 	fz_dropstream(file);
 cleanupbuf:
 	fz_dropbuffer(big);
-	return error;
+	return error; /* already rethrown */
 }
 
 static fz_error *
diff --git a/mupdf/pdf_pagetree.c b/mupdf/pdf_pagetree.c
index 47c0362b..eb02c1ed 100644
--- a/mupdf/pdf_pagetree.c
+++ b/mupdf/pdf_pagetree.c
@@ -177,7 +177,7 @@ cleanup:
 		fz_free(p->pobj);
 		fz_free(p);
 	}
-	return error;
+	return error; /* already rethrown */
 }
 
 int
diff --git a/mupdf/pdf_pattern.c b/mupdf/pdf_pattern.c
index c5668884..854bcf22 100644
--- a/mupdf/pdf_pattern.c
+++ b/mupdf/pdf_pattern.c
@@ -156,6 +156,6 @@ cleanupcsi:
 	pdf_dropcsi(csi);
 cleanup:
 	pdf_droppattern(pat);
-	return error;
+	return error; /* already rethrown */
 }
 
diff --git a/mupdf/pdf_repair.c b/mupdf/pdf_repair.c
index ffced0e0..ecdbf530 100644
--- a/mupdf/pdf_repair.c
+++ b/mupdf/pdf_repair.c
@@ -366,6 +366,6 @@ pdf_repairxref(pdf_xref *xref, char *filename)
 cleanup:
 	fz_dropstream(file);
 	fz_free(list);
-	return error;
+	return error; /* already rethrown */
 }
 
diff --git a/mupdf/pdf_save.c b/mupdf/pdf_save.c
index 1338493d..75c02e11 100644
--- a/mupdf/pdf_save.c
+++ b/mupdf/pdf_save.c
@@ -70,7 +70,7 @@ cleanupsrc:
 	fz_dropstream(srcstm);
 cleanupdst:
 	fz_dropstream(dststm);
-	return error;
+	return error; /* already rethrown */
 }
 
 static fz_error *
@@ -140,8 +140,8 @@ pdf_updatexref(pdf_xref *xref, char *path)
 			error = writeobject(out, xref, xref->crypt, oid, xref->table[oid].gen);
 			if (error)
 			{
-				error = fz_rethrow(error, "cannot write object (oid=%d)", oid);
-				goto cleanup;
+				fz_dropstream(out);
+				return fz_rethrow(error, "cannot write object (oid=%d)", oid);
 			}
 		}
 	}
@@ -212,12 +212,10 @@ pdf_updatexref(pdf_xref *xref, char *path)
 
 	xref->startxref = startxref;
 
-	fz_dropstream(out);
-	return fz_okay;
+	/* TODO: check for write errors */
 
-cleanup:
 	fz_dropstream(out);
-	return error;
+	return fz_okay;
 }
 
 fz_error *
@@ -272,8 +270,9 @@ pdf_savexref(pdf_xref *xref, char *path, pdf_crypt *encrypt)
 			error = writeobject(out, xref, encrypt, oid, x->type == 'o' ? 0 : x->gen);
 			if (error)
 			{
-				error = fz_rethrow(error, "cannot write object (oid=%d)", oid);
-				goto cleanup;
+				if (ofsbuf) fz_free(ofsbuf);
+				fz_dropstream(out);
+				return fz_rethrow(error, "cannot write object (oid=%d)", oid);
 			}
 		}
 		else
@@ -325,13 +324,10 @@ pdf_savexref(pdf_xref *xref, char *path, pdf_crypt *encrypt)
 
 	xref->startxref = startxref;
 
+	/* TODO: check for write errors */
+
 	if(ofsbuf) fz_free(ofsbuf);
 	fz_dropstream(out);
 	return fz_okay;
-
-cleanup:
-	if (ofsbuf) fz_free(ofsbuf);
-	fz_dropstream(out);
-	return error;
 }
 
diff --git a/mupdf/pdf_stream.c b/mupdf/pdf_stream.c
index a6cf696c..24d3d11b 100644
--- a/mupdf/pdf_stream.c
+++ b/mupdf/pdf_stream.c
@@ -346,7 +346,7 @@ cleanup1:
 	fz_dropobj(filters);
 cleanup0:
 	fz_dropfilter(base);
-	return error;
+	return error; /* already rethrown */
 }
 
 /*
diff --git a/mupdf/pdf_type3.c b/mupdf/pdf_type3.c
index 27ecfa3a..66537d2d 100644
--- a/mupdf/pdf_type3.c
+++ b/mupdf/pdf_type3.c
@@ -46,11 +46,11 @@ t3render(fz_glyph *glyph, fz_font *fzfont, int cid, fz_matrix trm)
 
 	error = fz_newrenderer(&gc, pdf_devicegray, 1, GCMEM);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot create renderer");
 	error = fz_rendertree(&pixmap, gc, tree, ctm, bbox, 0);
 	fz_droprenderer(gc);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot render glyph");
 
 	assert(pixmap->n == 1);
 
@@ -316,6 +316,6 @@ cleanup2:
 	fz_dropobj(resources);
 cleanup:
 	fz_dropfont((fz_font*)font);
-	return error;
+	return fz_rethrow(error, "cannot load type3 font");
 }
 
diff --git a/mupdf/pdf_unicode.c b/mupdf/pdf_unicode.c
index 2fb82233..dcb4e573 100644
--- a/mupdf/pdf_unicode.c
+++ b/mupdf/pdf_unicode.c
@@ -21,11 +21,14 @@ pdf_loadtounicode(pdf_font *font, pdf_xref *xref,
 
 		error = pdf_loadembeddedcmap(&cmap, xref, cmapstm);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot load embedded cmap");
 
 		error = pdf_newcmap(&font->tounicode);
 		if (error)
-			goto cleanup;
+		{
+			pdf_dropcmap(cmap);
+			return fz_rethrow(error, "cannot create tounicode cmap");
+		}
 
 		for (i = 0; i < (strings ? 256 : 65536); i++)
 		{
@@ -37,18 +40,23 @@ pdf_loadtounicode(pdf_font *font, pdf_xref *xref,
 				{
 					error = pdf_maprangetorange(font->tounicode, cid, cid, ucs);
 					if (error)
-						goto cleanup;
+					{
+						pdf_dropcmap(cmap);
+						return fz_rethrow(error, "cannot create tounicode mapping");
+					}
 				}
 			}
 		}
 
 		error = pdf_sortcmap(font->tounicode);
 		if (error)
-			goto cleanup;
+		{
+			pdf_dropcmap(cmap);
+			return fz_rethrow(error, "cannot sort tounicode mappings");
+		}
 
-	cleanup:
 		pdf_dropcmap(cmap);
-		return error;
+		return nil;
 	}
 
 	else if (collection)
@@ -56,15 +64,18 @@ pdf_loadtounicode(pdf_font *font, pdf_xref *xref,
 		pdf_logfont("tounicode cid collection\n");
 
 		if (!strcmp(collection, "Adobe-CNS1"))
-			return pdf_loadsystemcmap(&font->tounicode, "Adobe-CNS1-UCS2");
+			error = pdf_loadsystemcmap(&font->tounicode, "Adobe-CNS1-UCS2");
 		else if (!strcmp(collection, "Adobe-GB1"))
-			return pdf_loadsystemcmap(&font->tounicode, "Adobe-GB1-UCS2");
+			error = pdf_loadsystemcmap(&font->tounicode, "Adobe-GB1-UCS2");
 		else if (!strcmp(collection, "Adobe-Japan1"))
-			return pdf_loadsystemcmap(&font->tounicode, "Adobe-Japan1-UCS2");
+			error = pdf_loadsystemcmap(&font->tounicode, "Adobe-Japan1-UCS2");
 		else if (!strcmp(collection, "Adobe-Japan2"))
-			return pdf_loadsystemcmap(&font->tounicode, "Adobe-Japan2-UCS2");
+			error = pdf_loadsystemcmap(&font->tounicode, "Adobe-Japan2-UCS2");
 		else if (!strcmp(collection, "Adobe-Korea1"))
-			return pdf_loadsystemcmap(&font->tounicode, "Adobe-Korea1-UCS2");
+			error = pdf_loadsystemcmap(&font->tounicode, "Adobe-Korea1-UCS2");
+
+		if (error)
+			return fz_rethrow(error, "cannot load tounicode system cmap %s-UCS2", collection);
 	}
 
 	if (strings)
@@ -76,7 +87,7 @@ pdf_loadtounicode(pdf_font *font, pdf_xref *xref,
 		font->ncidtoucs = 256;
 		font->cidtoucs = fz_malloc(256 * sizeof(unsigned short));
 		if (!font->cidtoucs)
-			return fz_outofmem;
+			return fz_throw("outofmem: tounicode cidtoucs table");
 
 		for (i = 0; i < 256; i++)
 		{
@@ -111,7 +122,7 @@ pdf_newtextline(pdf_textline **linep)
 	pdf_textline *line;
 	line = *linep = fz_malloc(sizeof(pdf_textline));
 	if (!line)
-		return fz_outofmem;
+		return fz_throw("outofmem: textline struct");
 	line->len = 0;
 	line->cap = 0;
 	line->text = nil;
@@ -139,7 +150,7 @@ addtextchar(pdf_textline *line, fz_irect bbox, int c)
 		newcap = line->cap ? line->cap * 2 : 80;
 		newtext = fz_realloc(line->text, sizeof(pdf_textchar) * newcap);
 		if (!newtext)
-			return fz_outofmem;
+			return fz_throw("outofmem: textline buffer resize");
 		line->cap = newcap;
 		line->text = newtext;
 	}
@@ -219,7 +230,7 @@ extracttext(pdf_textline **line, fz_node *node, fz_matrix ctm)
 				pdf_textline *newline;
 				error = pdf_newtextline(&newline);
 				if (error)
-					return error;
+					return fz_rethrow(error, "cannot create new text line");
 				(*line)->next = newline;
 				*line = newline;
 			}
@@ -229,7 +240,7 @@ extracttext(pdf_textline **line, fz_node *node, fz_matrix ctm)
 				box.y0 = y; box.y1 = y;
 				error = addtextchar(*line, box, ' ');
 				if (error)
-					return error;
+					return fz_rethrow(error, "cannot add character to text line");
 			}
 
 			vx = fz_transformpoint(trm, vx);
@@ -248,7 +259,7 @@ extracttext(pdf_textline **line, fz_node *node, fz_matrix ctm)
 
 			error = addtextchar(*line, box, c);
 			if (error)
-				return error;
+				return fz_rethrow(error, "cannot add character to text line");
 		}
 	}
 
@@ -259,7 +270,7 @@ extracttext(pdf_textline **line, fz_node *node, fz_matrix ctm)
 	{
 		error = extracttext(line, node, ctm);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot extract text from display node");
 	}
 
 	return nil;
@@ -277,7 +288,7 @@ pdf_loadtextfromtree(pdf_textline **outp, fz_tree *tree, fz_matrix ctm)
 
 	error = pdf_newtextline(&root);
 	if (error)
-		return error;
+		return fz_rethrow(error, "cannot create new text line");
 
 	line = root;
 
@@ -285,7 +296,7 @@ pdf_loadtextfromtree(pdf_textline **outp, fz_tree *tree, fz_matrix ctm)
 	if (error)
 	{
 		pdf_droptextline(root);
-		return error;
+		return fz_rethrow(error, "cannot extract text from display tree");
 	}
 
 	*outp = root;
diff --git a/mupdf/pdf_xref.c b/mupdf/pdf_xref.c
index c9245bf0..7564855e 100644
--- a/mupdf/pdf_xref.c
+++ b/mupdf/pdf_xref.c
@@ -161,7 +161,7 @@ pdf_decryptxref(pdf_xref *xref)
 	{
 		error = pdf_resolve(&encrypt, xref);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot resolve /Encrypt object");
 
 		if (fz_isnull(encrypt))
 		{
diff --git a/stream/obj_dict.c b/stream/obj_dict.c
index a93ae1bd..a3366170 100644
--- a/stream/obj_dict.c
+++ b/stream/obj_dict.c
@@ -325,10 +325,13 @@ fz_dictputs(fz_obj *obj, char *key, fz_obj *val)
 	fz_error *error;
 	fz_obj *keyobj;
 	error = fz_newname(&keyobj, key);
-	if (error) return error;
+	if (error)
+		return fz_rethrow(error, "cannot create dict key");
 	error = fz_dictput(obj, keyobj, val);
 	fz_dropobj(keyobj);
-	return error;
+	if (error)
+		return fz_rethrow(error, "cannot insert dict entry");
+	return nil;
 }
 
 fz_error *
diff --git a/stream/obj_parse.c b/stream/obj_parse.c
index 316e8ad4..8f43a064 100644
--- a/stream/obj_parse.c
+++ b/stream/obj_parse.c
@@ -181,7 +181,7 @@ cleanup:
 	if (dict) fz_dropobj(dict);
 	*obj = nil;
 	*sp = s;
-	return error;
+	return error; /* already rethrown */
 }
 
 static fz_error *parsearray(fz_obj **obj, char **sp, struct vap *v)
@@ -462,7 +462,7 @@ static fz_error *parseobj(fz_obj **obj, char **sp, struct vap *v)
 		error = fz_throw("syntax error: unknown byte 0x%d", *s);
 
 	*sp = s;
-	return error;
+	return error; /* already rethrown */
 }
 
 fz_error *
@@ -476,12 +476,12 @@ fz_packobj(fz_obj **op, char *fmt, ...)
 	va_copy(v.ap, ap);
 
 	error = parseobj(op, &fmt, &v);
-	if (error)
-		error = fz_rethrow(error, "cannot parse object");
 
 	va_end(ap);
 
-	return error;
+	if (error)
+		return fz_rethrow(error, "cannot parse object");
+	return nil;
 }
 
 fz_error *
diff --git a/stream/stm_write.c b/stream/stm_write.c
index 23b268d9..9f136292 100644
--- a/stream/stm_write.c
+++ b/stream/stm_write.c
@@ -266,10 +266,10 @@ fz_printobj(fz_stream *file, fz_obj *obj, int tight)
 			return fz_throw("outofmem: scratch buffer");
 		fz_sprintobj(ptr, n, obj, tight);
 		error = fz_write(file, ptr, n);
-		if (error)
-			error = fz_rethrow(error, "cannot write buffer");
 		fz_free(ptr);
-		return error;
+		if (error)
+			return fz_rethrow(error, "cannot write buffer");
+		return fz_okay;
 	}
 }
 
@@ -303,11 +303,11 @@ fz_print(fz_stream *stm, char *fmt, ...)
 	va_end(ap);
 
 	error = fz_write(stm, p, n);
-	if (error)
-		error = fz_rethrow(error, "cannot write buffer");
 
 	fz_free(p);
 
-	return error;
+	if (error)
+		return fz_rethrow(error, "cannot write buffer");
+	return fz_okay;
 }
 
diff --git a/world/node_optimize.c b/world/node_optimize.c
index 69ca59cc..d284ce08 100644
--- a/world/node_optimize.c
+++ b/world/node_optimize.c
@@ -253,11 +253,11 @@ static fz_error *clean1x1(fz_node *node)
 				{
 					error = fz_newpixmap(&pix, 0, 0, 1, 1, image->n + 1);
 					if (error)
-						return error;
+						return fz_rethrow(error, "cannot create 1x1 pixmap");
 
 					error = image->loadtile(image, pix);
 					if (error)
-						return error;
+						return fz_rethrow(error, "cannot load pixmap tile");
 
 					for (i = 0; i < image->n; i++)
 						v[i] = pix->samples[i + 1] / 255.0;
@@ -266,10 +266,10 @@ static fz_error *clean1x1(fz_node *node)
 
 					error = fz_newsolidnode(&color, 1.0, image->cs, image->n, v);
 					if (error)
-						return error;
+						return fz_rethrow(error, "cannot create color node");
 					error = fz_newmasknode(&mask);
 					if (error)
-						return error;
+						return fz_rethrow(error, "cannot create mask node");
 
 					fz_insertnodeafter(current, mask);
 					fz_insertnodelast(mask, (fz_node*)rect);
@@ -290,7 +290,7 @@ static fz_error *clean1x1(fz_node *node)
 
 		error = clean1x1(current);
 		if (error)
-			return error;
+			return fz_rethrow(error, "cannot perform clean1x1 optimization");
 	}
 
 	return nil;