Test program below compiled with
gcc -Wall -O2 gio-test.c `pkg-config --libs --cflags glib-2.0 gio-2.0` 
./a.out 
size=1883

That file is more than 1883 bytes, however:
wget --debug http://www.gnumeric.org/
[...]
Content-Length: 5286
[...]

That's accurate:
ls -l ../../www-gnumeric-org/index.html 
-rw-r--r-- 1 welinder welinder 5286 Mar  3 19:49 ../../www-gnumeric-org/index.html


Here's what's wrong: gio, somehow, negotiates gzip content-encoding and
1883 is the size of that.



#include <glib.h>
#include <gio/gio.h>

int
main (int argc, char **argv)
{
	const char *uri = "http://www.gnumeric.org/";
	GFile *file = g_file_new_for_uri (uri);
	GFileInfo *info =
		g_file_query_info (file,
				   G_FILE_ATTRIBUTE_STANDARD_SIZE,
				   0, NULL, NULL);
	long filesize = g_file_info_get_size (info);
	g_printerr ("size=%ld\n", filesize);

	return 0;
}