GLib: cannot initialize GValue [...] the value has already been initialized as '(null)' - c

Question

I spot very strange behavior using a GValue:
This code runs fine:
#include <gtk/gtk.h>
int
main(int argc, char *argv[])
{
gtk_init(&argc, &argv);
{
GValue value;
g_value_init (&value, G_TYPE_STRING);
g_value_set_string (&value, "hallo");
gchar * strVal = g_strdup_value_contents (&value);
g_print ("gvalue: %s\n", strVal);
free (strVal);
g_value_unset (&value);
}
return 0;
}
However, the following code spawns the warning cannot initialize GValue with type 'gchararray', the value has already been initialized as '(null)' in the marked line.
Note, that the only thing, that's changed, is the new block with another GValue inside.
#include <gtk/gtk.h>
int
main(int argc, char *argv[])
{
gtk_init(&argc, &argv);
{
GValue value;
g_value_init (&value, G_TYPE_STRING);
g_value_set_string (&value, "hallo"); // warning spawns here
gchar * strVal = g_strdup_value_contents (&value);
g_print ("gvalue: %s\n", strVal);
free (strVal);
g_value_unset (&value);
}
{
GValue value2;
g_value_init (&value2, G_TYPE_INT);
g_value_set_int (&value2, 15);
gchar * strVal = g_strdup_value_contents (&value2);
g_print ("gvalue: %s\n", strVal);
free (strVal);
g_value_unset (&value2);
}
return 0;
}
Can someone tell me what is going on here?

Answer 1

You improperly initialized GValue.
GValue value = G_VALUE_INIT;
Not initialized variables at block scope have some garbage value, which may happen to be invalid and trigger an assertion (or may happen to be valid and nothing happens).