[PATCH 08/14] builtin_diff(): detect errors when parsing --unified argument

[Michael Haggerty <mhagger@alum.mit.edu>]

The previous code used strtoul() without any checks that it succeeded.
Instead use convert_l(), in strict mode, and die() if there is an
error. This tightens up the parsing:

* Leading whitespace is no longer allowed
* '+' and '-' are no longer allowed
* Trailing junk is not allowed

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 diff.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/diff.c b/diff.c
index abc32c8..a350677 100644
--- a/diff.c
+++ b/diff.c
@@ -2,6 +2,7 @@
  * Copyright (C) 2005 Junio C Hamano
  */
 #include "cache.h"
+#include "numparse.h"
 #include "quote.h"
 #include "diff.h"
 #include "diffcore.h"
@@ -2393,12 +2394,12 @@ static void builtin_diff(const char *name_a,
 			xecfg.flags |= XDL_EMIT_FUNCCONTEXT;
 		if (pe)
 			xdiff_set_find_func(&xecfg, pe->pattern, pe->cflags);
-		if (!diffopts)
-			;
-		else if (skip_prefix(diffopts, "--unified=", &v))
-			xecfg.ctxlen = strtoul(v, NULL, 10);
-		else if (skip_prefix(diffopts, "-u", &v))
-			xecfg.ctxlen = strtoul(v, NULL, 10);
+		if (diffopts
+		    && (skip_prefix(diffopts, "--unified=", &v) ||
+			skip_prefix(diffopts, "-u", &v))) {
+			if (convert_l(v, 10, &xecfg.ctxlen))
+				die("--unified argument must be a non-negative integer");
+		}
 		if (o->word_diff)
 			init_diff_words_data(&ecbdata, o, one, two);
 		xdi_diff_outf(&mf1, &mf2, fn_out_consume, &ecbdata,
-- 
2.1.4