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Problem with fscanf

I'm writing a Qt application which is using an old C-library named GLM. It is used to load vertex data from .obj-files. When reading the files it uses fscanf() to read out the numbers before storing these in some arrays.

Running an application using the library on a Ubuntu desktop works flawlessly, but when running on a real N900 device it reads out only the integers -1, 0 and 1 - which are not even the rounded equivalents of the floating point numbers in the file!

I could of course dive into reading the file using Qt instead, with hope that it would fix the problem, but I'm wondering if this is a common issue or whether it could be fixed in some other way?

Re: Problem with fscanf

It would be a big bug in libc if that really happened without any problems in the source code. Most probably, it's just a bad code. Do you have a small example of the fscanf call and a file on which it fails?

Re: Problem with fscanf

Quote:

Originally Posted by viraptor (Post 597036)

I was thinking it could have something to do with floating points on the N900, but I don't if that's an issue at all?

The relevant part of the code which does the reading is this:

Code:

while(fscanf(file, "%s", buf) != EOF) {

        switch(buf[0]) {

        case '#':                                /* comment */

            /* eat up rest of line */

            fgets(buf, sizeof(buf), file);

            break;

        case 'v':                                /* v, vn, vt */

            switch(buf[1]) {

            case '\0':                        /* vertex */

                fscanf(file, "%f %f %f",

                       &vertices[3 * numvertices + X],

                       &vertices[3 * numvertices + Y],

                       &vertices[3 * numvertices + Z]);

                numvertices++;

                break;

// ...

And the file looks somewhat like this (with a bunch of more values):

Code:

v 0.956776 2.407918 1.846345

v -1.020031 2.407918 1.846345

v 1.097976 2.223070 1.697290

v -1.161232 2.223070 1.697290

v 1.203877 2.096724 1.467326

v -1.267132 2.096724 1.467326

v 0.762625 1.936465 1.582468

v -0.825880 1.936465 1.582468

v 0.762625 2.094863 1.789404

v -0.825880 2.094863 1.789404

v 0.762625 2.343815 1.892402

v -0.825880 2.343815 1.892402

v 0.586125 2.419122 1.916050

v -0.649380 2.419122 1.916050

v 0.427274 2.242678 1.819275

v -0.490529 2.242678 1.819275

The source code I'm using is this:

http://www.cs.jhu.edu/~subodh/457/code/gltutor/glm.h
http://www.cs.jhu.edu/~subodh/457/code/gltutor/glm.c

In addition I'm printing the values to the console using this loop:

Code:

    for(int i = 0; i < numvertices; i++) {

        qDebug() << "out" << vertices[i];

    }

As mentioned, all values are kept as in the file when running the application on my desktop, but not on my N900.

Re: Problem with fscanf

A quick check (scanf("%f", &blah); printf("%f", blah);) shows that it should work. Maybe you can try your app with valgrind to make sure there are no strange overflows?
Are you printing the values out after the whole loop, or right after the scanf?

Re: Problem with fscanf

Hello,

as far as I know, scanf uses the current locale setting to determine
which char is used as "decimal_point".
You can view your locale settings with the command "locale".

With locale settings for germany for example:

Code:

 

~$ locale

LANG=de_DE

LC_CTYPE="de_DE"

LC_NUMERIC=de_DE

LC_TIME=de_DE

....

Code:

~ $ locale -ck decimal_point 

LC_NUMERIC

decimal_point =","

nicolai

Re: Problem with fscanf

@viraptor: Thanks for checking! You pointed me in the direction of the solution, which is the one nicolai mentions. I printed out the values with printf instead of qDebug() and I figured that printed it out with commas instead of dots.

@nicolai: Thanks a bunch for pointing that out :) My locale uses commas as decimal points, so that's exactly why it couldn't read the file. I'm using

Code:

setlocale(LC_NUMERIC, "en_US");

to set the locale to dots now.

Is this a good way to do this?