[Qemu-devel] [PATCH 41/56] json: Nicer recovery from invalid leading zero

[Markus Armbruster]

For input 0123, the lexer produces the tokens

    JSON_ERROR    01
    JSON_INTEGER  23

Reporting an error is correct; 0123 is invalid according to RFC 7159.
But the error recovery isn't nice.

Make the finite state machine eat digits before going into the error
state.  The lexer now produces

    JSON_ERROR    0123

Signed-off-by: Markus Armbruster <address@hidden>
---
 qobject/json-lexer.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/qobject/json-lexer.c b/qobject/json-lexer.c
index 7a82aab88b..f600cc732e 100644
--- a/qobject/json-lexer.c
+++ b/qobject/json-lexer.c
@@ -108,6 +108,7 @@ enum json_lexer_state {
     IN_SQ_STRING_ESCAPE,
     IN_SQ_STRING,
     IN_ZERO,
+    IN_BAD_ZERO,
     IN_DIGITS,
     IN_DIGIT,
     IN_EXP_E,
@@ -158,10 +159,14 @@ static const uint8_t json_lexer[][256] =  {
     /* Zero */
     [IN_ZERO] = {
         TERMINAL(JSON_INTEGER),
-        ['0' ... '9'] = IN_ERROR,
+        ['0' ... '9'] = IN_BAD_ZERO,
         ['.'] = IN_MANTISSA,
     },
 
+    [IN_BAD_ZERO] = {
+        ['0' ... '9'] = IN_BAD_ZERO,
+    },
+
     /* Float */
     [IN_DIGITS] = {
         TERMINAL(JSON_FLOAT),
-- 
2.17.1