Gcc compiler option to convert int arg to double?

Question

I made the assumption that int args passed for double parameters would be converted to doubles. For example

I am calling: make_line(root, "hi", 5,5,50,50);

on:

GooCanvasItem * make_line(GooCanvasItem * parent, char * name, gdouble x1, gdouble y1, gdouble x2, gdouble y2)
{
    printf("from make line: %f %f %f %f\n", x1, y1, x2, y2);
    //...
}

the printf produces:

from make line: 0.000000 0.000000 0.000000 0.000000

when I call it with

make_line(root, "hi", 5.0,5.0,50.0,50.0);

it gives the correct output.

Changing gdouble to double doesn't seem to fix the problem.

why would `5` be cast to `0`? it would cast to `5.0` if any. am I missing something? — none, Oct 25 '12 at 17:05
Sharing your code and the execution output would help us get the fact. In any case add(5) would not cast 'a' to 0. Please review your code. — Ayub, Oct 25 '12 at 17:10
Is the function prototype for `add` visible at the point where you're calling it? Are you compiling with `-Wall -Wextra -pedantic`? — Adam Rosenfield, Oct 25 '12 at 17:11

score 3 · Answer 1 · answered Oct 25 '12 at 17:10

3

a (5) won't be converted into 0.

I believe you are using %d in your printf instead of %f for printing double values. Turn on the compiler warnings when you compile your code.

Use -Wformat option of gcc.

answered Oct 25 '12 at 17:10

P.P

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@Ayub: In C standard, `%lf` -> `scanf`. – md5 Oct 25 '12 at 17:13
4

@Ayub Nope :) See: [Correct format specifier for double](http://stackoverflow.com/questions/4264127/correct-format-specifier-for-double-in-printf) – P.P Oct 25 '12 at 17:14
Thanks for the clarification. :) Good that many eyes are there to fix little mistakes. :D – Ayub Oct 25 '12 at 17:15
@mihajlv What's `gdouble`? how is it defined? – P.P Oct 25 '12 at 17:31
@mihajlv `Changing gdouble to double doesn't seem to fix the problem.` This can't be true. Here's the simplified demo: http://ideone.com/Bwan2d – P.P Oct 25 '12 at 17:39
@KingsIndian I know, it is wierd gdouble is just the c double used by glib, I think it has to do something with the glib library. – mihajlv Oct 25 '12 at 17:47

Gcc compiler option to convert int arg to double?

1 Answers1