Add a runtime check to see if parse_int64 needs to workaround sscanf bugs. If that...

diff --git a/json_util.c b/json_util.c
index 4e4e00c..194f290 100644 (file)
--- a/json_util.c
+++ b/json_util.c
@@ -61,6 +61,10 @@
 #include "json_tokener.h"
 #include "json_util.h"
 
+static int sscanf_is_broken = 0;
+static int sscanf_is_broken_testdone = 0;
+static void sscanf_is_broken_test(void);
+
 struct json_object* json_object_from_file(const char *filename)
 {
   struct printbuf *pb;
@@ -142,41 +146,78 @@ int json_object_to_file(char *filename, struct json_object *obj)
   return json_object_to_file_ext(filename, obj, JSON_C_TO_STRING_PLAIN);
 }
 
+/*
+ * Not all implementations of sscanf actually work properly.
+ * Check whether the one we're currently using does, and if
+ * it's broken, enable the workaround code.
+ */
+static void sscanf_is_broken_test()
+{
+       int64_t num64;
+
+       (void)sscanf(" -01234567890123456789012345", "%" SCNd64, &num64);
+       int ret_errno = errno;
+       int is_int64_min = (num64 == INT64_MIN);
+
+       (void)sscanf(" 01234567890123456789012345", "%" SCNd64, &num64);
+       int ret_errno2 = errno;
+       int is_int64_max = (num64 == INT64_MAX);
+
+       if (ret_errno != ERANGE || !is_int64_min ||
+           ret_errno2 != ERANGE || !is_int64_max)
+       {
+               MC_DEBUG("sscanf_is_broken_test failed, enabling workaround code\n");
+               sscanf_is_broken = 1;
+       }
+}
+
 int json_parse_int64(const char *buf, int64_t *retval)
 {
        int64_t num64;
-       const char *buf_skip_space;
+       const char *buf_sig_digits;
        int orig_has_neg;
        int saved_errno;
+
+       if (!sscanf_is_broken_testdone)
+       {
+               sscanf_is_broken_test();
+               sscanf_is_broken_testdone = 1;
+       }
+
+       // Skip leading spaces
+       while (isspace((int)*buf) && *buf)
+               buf++;
+
        errno = 0; // sscanf won't always set errno, so initialize
        if (sscanf(buf, "%" SCNd64, &num64) != 1)
        {
                MC_DEBUG("Failed to parse, sscanf != 1\n");
                return 1;
        }
+
        saved_errno = errno;
-       buf_skip_space = buf;
+       buf_sig_digits = buf;
        orig_has_neg = 0;
-       // Skip leading spaces
-       while (isspace((int)*buf_skip_space) && *buf_skip_space)
-               buf_skip_space++;
-       if (*buf_skip_space == '-')
+       if (*buf_sig_digits == '-')
        {
-               buf_skip_space++;
+               buf_sig_digits++;
                orig_has_neg = 1;
        }
-       // Skip leading zeros, but keep at least one digit
-       while (buf_skip_space[0] == '0' && buf_skip_space[1] != '\0')
-               buf_skip_space++;
-       if (buf_skip_space[0] == '0' && buf_skip_space[1] == '\0')
-               orig_has_neg = 0; // "-0" is the same as just plain "0"
-       
-       if (saved_errno != ERANGE)
+
+       // Not all sscanf implementations actually work
+       if (sscanf_is_broken && saved_errno != ERANGE)
        {
                char buf_cmp[100];
                char *buf_cmp_start = buf_cmp;
                int recheck_has_neg = 0;
                int buf_cmp_len;
+
+               // Skip leading zeros, but keep at least one digit
+               while (buf_sig_digits[0] == '0' && buf_sig_digits[1] != '\0')
+                       buf_sig_digits++;
+               if (num64 == 0) // assume all sscanf impl's will parse -0 to 0
+                       orig_has_neg = 0; // "-0" is the same as just plain "0"
+
                snprintf(buf_cmp_start, sizeof(buf_cmp), "%" PRId64, num64);
                if (*buf_cmp_start == '-')
                {
@@ -190,18 +231,22 @@ int json_parse_int64(const char *buf, int64_t *retval)
                 * If the sign is different, or
                 * some of the digits are different, or
                 * there is another digit present in the original string
-                * then we NOT successfully parsed the value.
+                * then we have NOT successfully parsed the value.
                 */
                if (orig_has_neg != recheck_has_neg ||
-                   strncmp(buf_skip_space, buf_cmp_start, strlen(buf_cmp_start)) != 0 ||
-                       ((int)strlen(buf_skip_space) != buf_cmp_len &&
-                        isdigit((int)buf_skip_space[buf_cmp_len])
+                   strncmp(buf_sig_digits, buf_cmp_start, strlen(buf_cmp_start)) != 0 ||
+                       ((int)strlen(buf_sig_digits) != buf_cmp_len &&
+                        isdigit((int)buf_sig_digits[buf_cmp_len])
                    )
                   )
                {
                        saved_errno = ERANGE;
                }
        }
+
+       // Not all sscanf impl's set the value properly when out of range.
+       // Always do this, even for properly functioning implementations,
+       // since it shouldn't slow things down much.
        if (saved_errno == ERANGE)
        {
                if (orig_has_neg)