How to set variable value from gtk_entry? - c

Question

I would like to set var pid from entry, but I got the following warning:
gtk.c:7:6: warning: assignment makes integer from pointer without a cast [enabled by default].
How I can make var pid == entry? It is very imporatant because this program is going to send signal to a process which id (pid) we are going to enter.
#include <gtk/gtk.h>
#include <stdlib.h>
pid_t pid;
void sendSighup(GtkWidget *widget,GtkWidget *entry, gpointer label) {
pid = gtk_entry_get_text(GTK_ENTRY(entry));
kill(pid,SIGHUP);
}
void sendSigint(GtkWidget *widget, gpointer label) {
kill(pid,SIGINT);
}
void sendSigkill(GtkWidget *widget, gpointer label) {
kill(pid,SIGKILL);
}
void sendSigterm(GtkWidget *widget, gpointer label) {
kill(pid,SIGTERM);
}
void sendSigstop(GtkWidget *widget, gpointer label) {
kill(pid,SIGSTOP);
}
accept_clicked (GtkButton *button, GObject *context_object)
{
GtkLabel *accept_lable1 = g_object_get_data (context_object, "label1");
GtkEntry *accept_entry = g_object_get_data (context_object, "entry");
const char *entry_in = gtk_entry_get_text (accept_entry);
gtk_label_set_text (accept_lable1, entry_in);
}
int main( int argc, char *argv[])
{
GtkWidget *window;
GtkWidget *frame;
GtkWidget *table;
GtkWidget *button1;
GtkWidget *button2;
GtkWidget *button3;
GtkWidget *button4;
GtkWidget *button5;
GtkWidget *quit;
GtkWidget *set;
GtkWidget *vseparator;
GtkWidget *entry;
GtkWidget *label;
GtkWidget *label1;
GtkWidget *label2;
gtk_init(&argc, &argv);
window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_window_set_title(GTK_WINDOW(window), "Send Signal");
gtk_window_set_default_size(GTK_WINDOW(window), 300, 250);
gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
frame = gtk_fixed_new();
gtk_container_add(GTK_CONTAINER(window), frame);
button1 = gtk_button_new_with_label("Sighup");
gtk_fixed_put(GTK_FIXED(frame), button1, 8, 15);
gtk_widget_set_size_request(button1, 80, 35);
button2 = gtk_button_new_with_label("Sigint");
gtk_fixed_put(GTK_FIXED(frame), button2, 8, 60);
gtk_widget_set_size_request(button2, 80, 35);
button3 = gtk_button_new_with_label("Sigkill");
gtk_fixed_put(GTK_FIXED(frame), button3, 8, 105);
gtk_widget_set_size_request(button3, 80, 35);
button4 = gtk_button_new_with_label("Sigterm");
gtk_fixed_put(GTK_FIXED(frame), button4, 8, 150);
gtk_widget_set_size_request(button4, 80, 35);
button5 = gtk_button_new_with_label("Sigstop");
gtk_fixed_put(GTK_FIXED(frame), button5, 8, 195);
gtk_widget_set_size_request(button5, 80, 35);
set = gtk_button_new_with_label ("Set");
gtk_fixed_put(GTK_FIXED(frame), set, 200, 80);
gtk_widget_set_size_request(set, 80, 35);
quit = gtk_button_new_with_label("Quit");
gtk_fixed_put(GTK_FIXED(frame), quit, 200, 195);
gtk_widget_set_size_request(quit, 80, 35);
vseparator = gtk_vseparator_new();
gtk_widget_set_size_request(vseparator, 10, 240);
gtk_fixed_put(GTK_FIXED(frame), vseparator, 95, 5);
label = gtk_label_new("Enter PID:");
gtk_fixed_put(GTK_FIXED(frame), label, 165, 20);
label2 = gtk_label_new("PID:");
gtk_fixed_put(GTK_FIXED(frame), label2, 110, 89);
label1 = gtk_label_new("0000");
gtk_fixed_put(GTK_FIXED(frame), label1, 140, 89);
entry = gtk_entry_new();
gtk_fixed_put(GTK_FIXED(frame), entry, 120, 40);
gtk_widget_grab_focus(entry);
g_object_set_data(G_OBJECT(set), "label1", label1);
g_object_set_data(G_OBJECT(set), "entry", entry);
g_signal_connect(GTK_BUTTON (set), "clicked",
G_CALLBACK (accept_clicked), set);
g_signal_connect_swapped(G_OBJECT(window), "destroy",
G_CALLBACK(gtk_main_quit), NULL);
g_signal_connect(button1, "clicked",
G_CALLBACK(sendSighup), NULL);
g_signal_connect(button2, "clicked",
G_CALLBACK(sendSigint), NULL);
g_signal_connect(button3, "clicked",
G_CALLBACK(sendSigkill), NULL);
g_signal_connect(button4, "clicked",
G_CALLBACK(sendSigterm), NULL);
g_signal_connect(button5, "clicked",
G_CALLBACK(sendSigstop), NULL);
g_signal_connect(G_OBJECT(quit), "clicked",
G_CALLBACK(gtk_main_quit), G_OBJECT(window));
gtk_widget_show_all(window);
gtk_widget_show(entry);
gtk_widget_show(label);
gtk_main();
return 0;
}

Answer 1

In that line you can either use the plain old atoi:
pid = atoi(gtk_entry_get_text(GTK_ENTRY(entry)));
or use a more complex function such as g-ascii-strtod.

Answer 2

gtk_entry_get_text returns char* - a pointer to char. You are assigning a pointer to char to int in your code. This is implementation-defined according to C standard and is not probably what you want, this is why your compiler gives you a warning:
6.3.2.3 p.6:
Any pointer type may be converted to an integer type. Except as
previously specified, the result is implementation-defined. If the
result cannot be represented in the integer type, the behavior is
undefined. The result need not be in the range of values of any
integer type.
For example, take a look at this code which is an exact representation of problem you have:
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
char *p ="123456";
int i = p;
printf("%d\n", i);
printf("%p\n", p);
exit 0;
}
It prints:
134514096
0x80485b0
Pointer to char is assigned to int in line 7. This yields the same error as in your code:
main.c:7:17: warning: initialization makes integer from pointer
without a cast [enabled by default]
Now let's see what's the result of this assignment - do not forget that this an implementation-defined behavior. First printf prints value of i variable after assignment. Second printf prints an address that a pointer holds using %p specifier which prints a pointer value in an implementation-defined manner. These values turned out to be the same - 0x80485b0 is hexadecimal 134514096. What happened here is pointer value (that is an address) has been assigned to int. The same is happening in your code. C is a very simple language, it doesn't do anything behind your back. It will not automatically convert a series of digits written in a string to an int. To convert string to a number you need to use standard atoi function or a custom function provided by libraries you are using.