It's better to give downstream clients a valid JSON string,
even if they are semantically expecting a number, than it is
to give them a bare keyword extension that can cause a
lexical error.
Of course, as long as we don't recognize (certain) strings as valid
numbers during a conversion to QObject, this means our extension
of accepting bare keywords for non-finite numbers cannot undergo
a round trip (once converted into a string, we never get back to
a QFloat). However, non-finite input is rare enough that it's
not worth bothering with at the moment.
Signed-off-by: Eric Blake <ebl...@redhat.com>
---
qobject/qjson.c | 15 ++++++++++++---
tests/check-qjson.c | 11 +++++------
docs/qmp-spec.txt | 2 +-
3 files changed, 18 insertions(+), 10 deletions(-)
diff --git a/qobject/qjson.c b/qobject/qjson.c
index ef160d2..465b080 100644
--- a/qobject/qjson.c
+++ b/qobject/qjson.c
@@ -12,6 +12,7 @@
*/
#include "qemu/osdep.h"
+#include <math.h>
#include "qapi/qmp/json-lexer.h"
#include "qapi/qmp/json-parser.h"
#include "qapi/qmp/json-streamer.h"
@@ -236,19 +237,27 @@ static void to_json(const QObject *obj, QString *str, int
pretty, int indent)
}
case QTYPE_QFLOAT: {
QFloat *val = qobject_to_qfloat(obj);
+ double d = qfloat_get_double(val);
char buffer[1024];
int len;
+ if (!isfinite(d)) {
+ /* Always output valid JSON - a semantic error due to a
+ * string where a number was expected is better than a
+ * lexical error from a strict parser */
+ snprintf(buffer, sizeof(buffer), "\"%f\"", d);
+ qstring_append(str, buffer);
+ break;
+ }
+
/* FIXME: snprintf() is locale dependent; but JSON requires
* numbers to be formatted as if in the C locale. Dependence
* on C locale is a pervasive issue in QEMU. */
- /* FIXME: This risks printing Inf or NaN, which are not valid
- * JSON values. */
/* FIXME: the default precision of 6 for %f often causes
* rounding errors; we should be using DBL_DECIMAL_DIG (17),
* and only rounding to a shorter number if the result would
* still produce the same floating point value. */
- len = snprintf(buffer, sizeof(buffer), "%f", qfloat_get_double(val));
+ len = snprintf(buffer, sizeof(buffer), "%f", d);
while (len > 0 && buffer[len - 1] == '0') {
len--;
}
diff --git a/tests/check-qjson.c b/tests/check-qjson.c
index 95adf64..b0a9178 100644
--- a/tests/check-qjson.c
+++ b/tests/check-qjson.c
@@ -974,12 +974,12 @@ static void non_finite_number(void)
double decoded;
const char *canonical;
} test_cases[] = {
- { "nan", NAN },
- { "NaN", NAN, "nan" },
+ { "nan", NAN, "\"nan\"" },
+ { "NaN", NAN, "\"nan\"" },
/* Not all libc implementations can round-trip '-nan' */
/* We do not support forms like 'NAN(0)' */
- { "inf", INFINITY },
- { "-INFINITY", -INFINITY, "-inf" },
+ { "inf", INFINITY, "\"inf\"" },
+ { "-INFINITY", -INFINITY, "\"-inf\"" },
{ },
};
@@ -1002,8 +1002,7 @@ static void non_finite_number(void)
}
str = qobject_to_json(obj);
- g_assert_cmpstr(qstring_get_str(str), ==,
- test_cases[i].canonical ?: test_cases[i].encoded);
+ g_assert_cmpstr(qstring_get_str(str), ==, test_cases[i].canonical);
QDECREF(str);
QDECREF(qfloat);
}
diff --git a/docs/qmp-spec.txt b/docs/qmp-spec.txt
index bfba431..75c68d9 100644
--- a/docs/qmp-spec.txt
+++ b/docs/qmp-spec.txt
@@ -53,7 +53,7 @@ double quoting on output.
As an extension, the server understands case-insensitive forms of
non-finite numbers, such as "NaN", "Inf", and "-infinity" (but not
-"NaN(...)").
+"NaN(...)"); however, such numbers are output as a json-string.
2.1 General Definitions
-----------------------
--
2.5.5
