Re: libc/printf bug

On a sunny day (27 Feb 2006 12:09:54 -0800) it happened "bill pursell"
<bill.pursell@xxxxxxxxx> wrote in
<1141070994.179527.261050@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

The following code exhibits unexpected behavior. Either it's
a bug in libc, or the author (me) is blind as a bat. Am I missing
something here, or is something horribly wrong? It appears
that printf is mangling the address unless the second argument
gets cast. I don't see that the cast should have any effect at all
on the output. Any thoughts?

[tmp]$ cat printf_bug.c


int
main()
{

float a=0;

printf("%p\n", &a);
printf("%x %p\n", a, &a);
printf("%x %p\n", (int)a, &a);
}
[tmp]$ ./a.out
0xfefb6764
0 (nil)
0 0xfefb6764
[tmp]$

How would you print a float in hex? I think print will convert it to integer, and that is 0.
`%x', `%X'
Print an integer as an unsigned hexadecimal number. `%x' uses
lower-case letters and `%X' uses upper-case. *Note Integer
Conversions::, for details.
So seems printf gets confused because you present it with a float when i t wants an integer.
This behavior I have seen in other cases where wrong or missing arguments were presented too.
Maybe it has to do with stack space where the vars are when the function is called?

.

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