Move from volatile to fz_var.

When using exceptions (which are implemented using setjmp/longjmp), we
need to be careful to ensure that variable values get written back
before any exception happens.

Previously we've done that using volatile, but that produces nasty
warnings (and unduly limits the compilers freedom to optimise). Here
we introduce a new macro fz_var that passes the address of the variable
out of scope. This means that the compiler has to ensure that any
changes to its value are written back to memory before calling any
out of scope function.

11 files changed, 86 insertions, 33 deletions

diff --git a/fitz/base_error.c b/fitz/base_error.c
index b844fb6a..bd6801eb 100644
--- a/fitz/base_error.c
+++ b/fitz/base_error.c
@@ -2,6 +2,11 @@
 
 /* Warning context */
 
+void fz_var_imp(void *var)
+{
+	var = var; /* Do nothing */
+}
+
 void fz_flush_warnings(fz_context *ctx)
 {
 	if (ctx->warn->count > 1)
diff --git a/fitz/fitz.h b/fitz/fitz.h
index 70d14086..09c12c14 100644
--- a/fitz/fitz.h
+++ b/fitz/fitz.h
@@ -162,6 +162,9 @@ struct fz_error_context_s
 	char message[256];
 };
 
+void fz_var_imp(void *);
+#define fz_var(var) fz_var_imp((void *)&(var))
+
 #define fz_try(ctx) \
 	if (fz_push_try(ctx->error), \
 		!setjmp(ctx->error->stack[ctx->error->top].buffer)) \
diff --git a/pdf/pdf_font.c b/pdf/pdf_font.c
index 3a94527b..b33cbbc0 100644
--- a/pdf/pdf_font.c
+++ b/pdf/pdf_font.c
@@ -391,7 +391,7 @@ pdf_load_simple_font(pdf_xref *xref, fz_obj *dict)
 	fz_obj *encoding;
 	fz_obj *widths;
 	unsigned short *etable = NULL;
-	pdf_font_desc * volatile fontdesc;
+	pdf_font_desc *fontdesc;
 	FT_Face face;
 	FT_CharMap cmap;
 	int symbolic;
@@ -405,6 +405,8 @@ pdf_load_simple_font(pdf_xref *xref, fz_obj *dict)
 	int fterr;
 	fz_context *ctx = xref->ctx;
 
+	fz_var(fontdesc);
+
 	basefont = fz_to_name(fz_dict_gets(dict, "BaseFont"));
 	fontname = clean_font_name(basefont);
 
@@ -696,7 +698,7 @@ load_cid_font(pdf_xref *xref, fz_obj *dict, fz_obj *encoding, fz_obj *to_unicode
 {
 	fz_obj *widths;
 	fz_obj *descriptor;
-	pdf_font_desc * volatile fontdesc;
+	pdf_font_desc *fontdesc;
 	FT_Face face;
 	int kind;
 	char collection[256];
@@ -706,6 +708,8 @@ load_cid_font(pdf_xref *xref, fz_obj *dict, fz_obj *encoding, fz_obj *to_unicode
 	int dw;
 	fz_context *ctx = xref->ctx;
 
+	fz_var(fontdesc);
+
 	fz_try(ctx)
 	{
 		/* Get font name and CID collection */
diff --git a/pdf/pdf_function.c b/pdf/pdf_function.c
index 3ef0d75f..82c29dfd 100644
--- a/pdf/pdf_function.c
+++ b/pdf/pdf_function.c
@@ -817,13 +817,15 @@ parse_code(pdf_function *func, fz_stream *stream, int *codeptr)
 static void
 load_postscript_func(pdf_function *func, pdf_xref *xref, fz_obj *dict, int num, int gen)
 {
-	fz_stream * volatile stream = NULL;
+	fz_stream *stream = NULL;
 	int codeptr;
 	char buf[64];
 	int tok;
 	int len;
 	fz_context *ctx = xref->ctx;
 
+	fz_var(stream);
+
 	fz_try(ctx)
 	{
 		stream = pdf_open_stream(xref, num, gen);
@@ -1328,7 +1330,7 @@ pdf_function *
 pdf_load_function(pdf_xref *xref, fz_obj *dict)
 {
 	fz_context *ctx = xref->ctx;
-	pdf_function * volatile func;
+	pdf_function *func;
 	fz_obj *obj;
 	int i;
 
diff --git a/pdf/pdf_image.c b/pdf/pdf_image.c
index b8785cf4..f8c4277c 100644
--- a/pdf/pdf_image.c
+++ b/pdf/pdf_image.c
@@ -28,25 +28,31 @@ pdf_mask_color_key(fz_pixmap *pix, int n, int *colorkey)
 static fz_pixmap *
 pdf_load_image_imp(pdf_xref *xref, fz_obj *rdb, fz_obj *dict, fz_stream *cstm, int forcemask)
 {
-	fz_stream * volatile stm = NULL;
-	fz_pixmap * volatile tile = NULL;
+	fz_stream *stm = NULL;
+	fz_pixmap *tile = NULL;
 	fz_obj *obj, *res;
 
 	int w, h, bpc, n;
 	int imagemask;
 	int interpolate;
 	int indexed;
-	fz_colorspace * volatile colorspace = NULL;
-	fz_pixmap * volatile mask = NULL; /* explicit mask/softmask image */
+	fz_colorspace *colorspace = NULL;
+	fz_pixmap *mask = NULL; /* explicit mask/softmask image */
 	int usecolorkey;
 	int colorkey[FZ_MAX_COLORS * 2];
 	float decode[FZ_MAX_COLORS * 2];
 
 	int stride;
-	unsigned char * volatile samples = NULL;
+	unsigned char *samples = NULL;
 	int i, len;
 	fz_context *ctx = xref->ctx;
 
+	fz_var(stm);
+	fz_var(tile);
+	fz_var(colorspace);
+	fz_var(mask);
+	fz_var(samples);
+
 	fz_try(ctx)
 	{
 		/* special case for JPEG2000 images */
@@ -285,12 +291,15 @@ pdf_is_jpx_image(fz_context *ctx, fz_obj *dict)
 static fz_pixmap *
 pdf_load_jpx_image(pdf_xref *xref, fz_obj *dict)
 {
-	fz_buffer * volatile buf = NULL;
-	fz_colorspace * volatile colorspace = NULL;
+	fz_buffer *buf = NULL;
+	fz_colorspace *colorspace = NULL;
 	fz_pixmap *img;
 	fz_obj *obj;
 	fz_context *ctx = xref->ctx;
 
+	fz_var(buf);
+	fz_var(colorspace);
+
 	buf = pdf_load_stream(xref, fz_to_num(dict), fz_to_gen(dict));
 	/* RJW: "cannot load jpx image data" */
 
@@ -307,7 +316,10 @@ pdf_load_jpx_image(pdf_xref *xref, fz_obj *dict)
 		/* RJW: "cannot load jpx image" */
 
 		if (colorspace)
+		{
 			fz_drop_colorspace(ctx, colorspace);
+			colorspace = NULL;
+		}
 		fz_drop_buffer(ctx, buf);
 		buf = NULL;
 
diff --git a/pdf/pdf_interpret.c b/pdf/pdf_interpret.c
index 6d312724..b82b4297 100644
--- a/pdf/pdf_interpret.c
+++ b/pdf/pdf_interpret.c
@@ -2452,10 +2452,13 @@ pdf_run_buffer(pdf_csi *csi, fz_obj *rdb, fz_buffer *contents)
 {
 	fz_context *ctx = csi->dev->ctx;
 	int len = sizeof csi->xref->scratch;
-	char * volatile buf = NULL;
-	fz_stream * volatile file = NULL;
+	char *buf = NULL;
+	fz_stream * file = NULL;
 	int save_in_text;
 
+	fz_var(buf);
+	fz_var(file);
+
 	fz_try(ctx)
 	{
 		buf = fz_malloc(ctx, len); /* we must be re-entrant for type3 fonts */
diff --git a/pdf/pdf_parse.c b/pdf/pdf_parse.c
index 6b7fdb12..7174c23a 100644
--- a/pdf/pdf_parse.c
+++ b/pdf/pdf_parse.c
@@ -302,14 +302,18 @@ end:
 fz_obj *
 pdf_parse_dict(pdf_xref *xref, fz_stream *file, char *buf, int cap)
 {
-	fz_obj * volatile dict = NULL;
-	fz_obj * volatile key = NULL;
-	fz_obj * volatile val = NULL;
+	fz_obj *dict = NULL;
+	fz_obj *key = NULL;
+	fz_obj *val = NULL;
 	int tok;
 	int len;
 	int a, b;
 	fz_context *ctx = file->ctx;
 
+	fz_var(dict);
+	fz_var(key);
+	fz_var(val);
+
 	dict = fz_new_dict(ctx, 8);
 
 	fz_try(ctx)
@@ -430,13 +434,15 @@ pdf_parse_ind_obj(pdf_xref *xref,
 	fz_stream *file, char *buf, int cap,
 	int *onum, int *ogen, int *ostmofs)
 {
-	fz_obj * volatile obj = NULL;
+	fz_obj *obj = NULL;
 	int num = 0, gen = 0, stm_ofs;
 	int tok;
 	int len;
 	int a, b;
 	fz_context *ctx = file->ctx;
 
+	fz_var(obj);
+
 	tok = pdf_lex(file, buf, cap, &len);
 	/* RJW: cannot parse indirect object (%d %d R)", num, gen */
 	if (tok != PDF_TOK_INT)
diff --git a/pdf/pdf_repair.c b/pdf/pdf_repair.c
index 7930b5b5..bfa89751 100644
--- a/pdf/pdf_repair.c
+++ b/pdf/pdf_repair.c
@@ -192,12 +192,12 @@ pdf_repair_xref(pdf_xref *xref, char *buf, int bufsize)
 	fz_obj *dict, *obj;
 	fz_obj *length;
 
-	fz_obj * volatile encrypt = NULL;
-	fz_obj * volatile id = NULL;
-	fz_obj * volatile root = NULL;
-	fz_obj * volatile info = NULL;
+	fz_obj *encrypt = NULL;
+	fz_obj *id = NULL;
+	fz_obj *root = NULL;
+	fz_obj *info = NULL;
 
-	struct entry * volatile list = NULL;
+	struct entry *list = NULL;
 	int listlen;
 	int listcap;
 	int maxnum = 0;
@@ -211,6 +211,12 @@ pdf_repair_xref(pdf_xref *xref, char *buf, int bufsize)
 	int i, n, c;
 	fz_context *ctx = xref->ctx;
 
+	fz_var(encrypt);
+	fz_var(id);
+	fz_var(root);
+	fz_var(info);
+	fz_var(list);
+
 	fz_seek(xref->file, 0, 0);
 
 	fz_try(ctx)
diff --git a/pdf/pdf_shade.c b/pdf/pdf_shade.c
index b281542b..3803f77e 100644
--- a/pdf/pdf_shade.c
+++ b/pdf/pdf_shade.c
@@ -960,15 +960,19 @@ pdf_load_type7_shade(fz_shade *shade, pdf_xref *xref, fz_obj *dict,
 static fz_shade *
 pdf_load_shading_dict(pdf_xref *xref, fz_obj *dict, fz_matrix transform)
 {
-	fz_shade * volatile shade = NULL;
-	pdf_function * volatile func[FZ_MAX_COLORS] = { NULL };
-	fz_stream * volatile stream = NULL;
+	fz_shade *shade = NULL;
+	pdf_function *func[FZ_MAX_COLORS] = { NULL };
+	fz_stream *stream = NULL;
 	fz_obj *obj;
 	int funcs;
 	int type;
 	int i;
 	fz_context *ctx = xref->ctx;
 
+	fz_var(shade);
+	fz_var(func);
+	fz_var(stream);
+
 	fz_try(ctx)
 	{
 		shade = fz_malloc(ctx, sizeof(fz_shade));
diff --git a/pdf/pdf_stream.c b/pdf/pdf_stream.c
index 614f076a..0a38d20f 100644
--- a/pdf/pdf_stream.c
+++ b/pdf/pdf_stream.c
@@ -228,9 +228,11 @@ pdf_open_inline_stream(fz_stream *chain, pdf_xref *xref, fz_obj *stmobj, int len
 fz_stream *
 pdf_open_raw_stream(pdf_xref *xref, int num, int gen)
 {
-	pdf_xref_entry * volatile x;
+	pdf_xref_entry *x;
 	fz_stream *stm;
 
+	fz_var(x);
+
 	if (num < 0 || num >= xref->len)
 		fz_throw(xref->ctx, "object id out of range (%d %d R)", num, gen);
 
@@ -341,7 +343,9 @@ pdf_load_stream(pdf_xref *xref, int num, int gen)
 	fz_stream *stm;
 	fz_obj *dict, *obj;
 	int i, len, n;
-	fz_buffer * volatile buf;
+	fz_buffer *buf;
+
+	fz_var(buf);
 
 	stm = pdf_open_stream(xref, num, gen);
 	/* RJW: "cannot open stream (%d %d R)", num, gen */
diff --git a/pdf/pdf_xref.c b/pdf/pdf_xref.c
index d391e55c..b447dde6 100644
--- a/pdf/pdf_xref.c
+++ b/pdf/pdf_xref.c
@@ -297,7 +297,7 @@ static fz_obj *
 pdf_read_new_xref(pdf_xref *xref, char *buf, int cap)
 {
 	fz_stream *stm;
-	fz_obj * volatile trailer = NULL;
+	fz_obj *trailer = NULL;
 	fz_obj *index = NULL;
 	fz_obj *obj = NULL;
 	int num, gen, stm_ofs;
@@ -305,6 +305,8 @@ pdf_read_new_xref(pdf_xref *xref, char *buf, int cap)
 	int t;
 	fz_context *ctx = xref->ctx;
 
+	fz_var(trailer);
+
 	fz_try(ctx)
 	{
 		trailer = pdf_parse_ind_obj(xref, xref->file, buf, cap, &num, &gen, &stm_ofs);
@@ -579,9 +581,11 @@ pdf_read_ocg(pdf_xref *xref)
 {
 	fz_obj *obj, *ocg;
 	int len, i;
-	pdf_ocg_descriptor * volatile desc;
+	pdf_ocg_descriptor *desc;
 	fz_context *ctx = xref->ctx;
 
+	fz_var(desc);
+
 	obj = fz_dict_gets(fz_dict_gets(xref->trailer, "Root"), "OCProperties");
 	if (obj == NULL)
 		return;
@@ -844,8 +848,8 @@ pdf_load_obj_stm(pdf_xref *xref, int num, int gen, char *buf, int cap)
 {
 	fz_stream *stm;
 	fz_obj *objstm;
-	int * volatile numbuf = NULL;
-	int * volatile ofsbuf = NULL;
+	int *numbuf = NULL;
+	int *ofsbuf = NULL;
 
 	fz_obj *obj;
 	int first;
@@ -854,8 +858,8 @@ pdf_load_obj_stm(pdf_xref *xref, int num, int gen, char *buf, int cap)
 	int tok;
 	fz_context *ctx = xref->ctx;
 
-	//fz_var(numbuf);
-	//fz_var(ofsbuf);
+	fz_var(numbuf);
+	fz_var(ofsbuf);
 	fz_try(ctx)
 	{
 		objstm = pdf_load_object(xref, num, gen);