RE: impossible to print floats with snprintf

lecozahu — Thu, 12 Nov 2020 15:11:47 GMT

Hi !

I am sincerely sorry but everything is back to normal. I had to change a setting which removed the bug.
I still send you my code in case you are interested.

the output was:
...
position:; ; ;

}

and my code was:

static char buffer_json[2048];
static double longitude;
static double latitude;
static double altitude;

int encode_JSON_data(char *const why)
{       
        
        int buffer_length = 0;
        buffer_json[0] = '\0';
        
        char * sn = "005115541";
        


        buffer_length += snprintf(buffer_json + buffer_length, sizeof(buffer_json) - buffer_length, "{\n");
        buffer_length += snprintf(buffer_json + buffer_length, sizeof(buffer_json) - buffer_length, "  \"SN\": \"%d\",\n", sn);
        buffer_length += snprintf(buffer_json + buffer_length, sizeof(buffer_json) - buffer_length, "  \"what\": \"%s\",\n", why);
        buffer_length += snprintf(buffer_json + buffer_length, sizeof(buffer_json) - buffer_length, "  \"position\": \"%f;%f;%0.1f\"\n", latitude, longitude,altitude);
        buffer_length += snprintf(buffer_json + buffer_length, sizeof(buffer_json) - buffer_length, "}");

        // vérifications de base
        if ((buffer_length >= (sizeof(buffer_json) - 1)) || buffer_json[buffer_length - 1] != '}')
        {
            LOG_ERR("JSON buffer overload.");
            return 0;
        }else 
        {
            return 1;
        }

}

Thank you for your reply,

Best regards,

Lecozahu

RE: impossible to print floats with snprintf

Heidi — Thu, 12 Nov 2020 12:29:33 GMT

Hi!

Could you provide a code snippet and the corresponding output?

The ticket you referenced is about the nRF5 SDK, and you're using NCS, which is why you don't have those configurations.

Note: a usual pitfall with snprintf is to design code that assumes the function returns the number of characters written to the buffer. The number returned is actually just the number of characters in the resulting string. If the resulting string is longer than size(buf) - 1 characters, the remaining characters are discarded and not stored but counted for in the functions return value.

The FPU should be enabled by its dependencies (CPU_HAS_FPU && ARM).