Move to exception handling rather than error passing throughout.

This frees us from passing errors back everywhere, and hence enables us
to pass results back as return values.

Rather than having to explicitly check for errors everywhere and bubble
them, we now allow exception handling to do the work for us; the
downside to this is that we no longer emit as much debugging information
as we did before (though this could be put back in). For now, the
debugging information we have lost has been retained in comments
with 'RJW:' at the start.

This code needs fuller testing, but is being committed as a work in
progress.

1 files changed, 48 insertions, 24 deletions

diff --git a/apps/pdfclean.c b/apps/pdfclean.c
index 4b5fa139..4b76afa2 100644
--- a/apps/pdfclean.c
+++ b/apps/pdfclean.c
@@ -287,13 +287,17 @@ static void renumberobjs(void)
 
 static void retainpages(int argc, char **argv)
 {
-	fz_error error;
 	fz_obj *oldroot, *root, *pages, *kids, *countobj, *parent;
 
 	/* Load the old page tree */
-	error = pdf_load_page_tree(xref);
-	if (error)
-		die(fz_error_note(error, "cannot load page tree"));
+	fz_try(xref->ctx)
+	{
+		pdf_load_page_tree(xref);
+	}
+	fz_catch(xref->ctx)
+	{
+		die(fz_error_note(1, "cannot load page tree"));
+	}
 
 	/* Keep only pages/type entry to avoid references to unretained pages */
 	oldroot = fz_dict_gets(xref->trailer, "Root");
@@ -377,7 +381,6 @@ static void retainpages(int argc, char **argv)
 
 static void preloadobjstms(void)
 {
-	fz_error error;
 	fz_obj *obj;
 	int num;
 
@@ -385,9 +388,14 @@ static void preloadobjstms(void)
 	{
 		if (xref->table[num].type == 'o')
 		{
-			error = pdf_load_object(&obj, xref, num, 0);
-			if (error)
-				die(error);
+			fz_try(ctx)
+			{
+				obj = pdf_load_object(xref, num, 0);
+			}
+			fz_catch(ctx)
+			{
+				die(1);
+			}
 			fz_drop_obj(obj);
 		}
 	}
@@ -488,13 +496,17 @@ static void addhexfilter(fz_obj *dict)
 
 static void copystream(fz_obj *obj, int num, int gen)
 {
-	fz_error error;
 	fz_buffer *buf, *tmp;
 	fz_obj *newlen;
 
-	error = pdf_load_raw_stream(&buf, xref, num, gen);
-	if (error)
-		die(error);
+	fz_try(ctx)
+	{
+		buf = pdf_load_raw_stream(xref, num, gen);
+	}
+	fz_catch(ctx)
+	{
+		die(1);
+	}
 
 	if (doascii && isbinarystream(buf))
 	{
@@ -520,13 +532,17 @@ static void copystream(fz_obj *obj, int num, int gen)
 
 static void expandstream(fz_obj *obj, int num, int gen)
 {
-	fz_error error;
 	fz_buffer *buf, *tmp;
 	fz_obj *newlen;
 
-	error = pdf_load_stream(&buf, xref, num, gen);
-	if (error)
-		die(error);
+	fz_try(ctx)
+	{
+		buf = pdf_load_stream(xref, num, gen);
+	}
+	fz_catch(ctx)
+	{
+		die(1);
+	}
 
 	fz_dict_dels(obj, "Filter");
 	fz_dict_dels(obj, "DecodeParms");
@@ -555,13 +571,17 @@ static void expandstream(fz_obj *obj, int num, int gen)
 
 static void writeobject(int num, int gen)
 {
-	fz_error error;
 	fz_obj *obj;
 	fz_obj *type;
 
-	error = pdf_load_object(&obj, xref, num, gen);
-	if (error)
-		die(error);
+	fz_try(ctx)
+	{
+		obj = pdf_load_object(xref, num, gen);
+	}
+	fz_catch(ctx)
+	{
+		die(1);
+	}
 
 	/* skip ObjStm and XRef objects */
 	if (fz_is_dict(obj))
@@ -686,7 +706,6 @@ static void writepdf(void)
 
 int main(int argc, char **argv)
 {
-	fz_error error;
 	char *infile;
 	char *outfile = "out.pdf";
 	char *password = "";
@@ -724,9 +743,14 @@ int main(int argc, char **argv)
 	if (ctx == NULL)
 		die(fz_error_note(1, "failed to initialise context"));
 
-	error = pdf_open_xref(ctx, &xref, infile, password);
-	if (error)
-		die(fz_error_note(error, "cannot open input file '%s'", infile));
+	fz_try(ctx)
+	{
+		xref = pdf_open_xref(ctx, infile, password);
+	}
+	fz_catch(ctx)
+	{
+		die(fz_error_note(1, "cannot open input file '%s'", infile));
+	}
 
 	out = fopen(outfile, "wb");
 	if (!out)