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glib.h - GLib Core Utility Library

Category: 📂 glib/ (Third-Party Ecosystem) Header: <glib.h> Scope: GNOME / Cross-platform C Utility

The glib.h header is the entry point for GLib, a general-purpose utility library that provides advanced data structures, type wrappers, and the main event loop used by GTK applications.

Facilities Overview

Facility Category Key Symbols Description
Memory Mgmt g_malloc, g_free Safe memory allocation wrappers.
Linked Lists GList, g_list_append, g_list_free Doubly linked lists.
Strings GString, g_strdup, g_str_equal String manipulation and dynamic buffers.
Event Loop GMainLoop, g_main_loop_run Main event loop for async programming.
Error Handling GError, g_set_error Standardized error reporting mechanism.

Types & Variables

GList

typedef struct _GList GList;
struct _GList {
  gpointer data;
  GList *next;
  GList *prev;
};

Structure for a doubly linked list.

GString

typedef struct _GString GString;
struct _GString {
  gchar  *str;
  gsize   len;
  gsize   allocated_len;
};

Dynamically growing string buffer.

GError

typedef struct _GError GError;
struct _GError {
  GQuark       domain;
  gint         code;
  gchar       *message;
};

Standard mechanism for returning errors from functions.

GMainLoop

typedef struct _GMainLoop GMainLoop;

Opaque structure representing a main event loop.

Functions

Memory Management

g_malloc

gpointer g_malloc(gsize n_bytes)

Allocates n_bytes of memory. If the allocation fails, the application is terminated.

Returns: A pointer to the allocated memory.

g_free

void g_free(gpointer mem)

Frees the memory pointed to by mem. If mem is NULL, it does nothing.

Linked Lists

g_list_append

GList *g_list_append(GList *list, gpointer data)

Adds a new element to the end of the list.

Returns: The new start of the GList.

Example 
#include <glib.h>
#include <stdio.h>

int main(void) {
    GList *list = NULL;
    list = g_list_append(list, "Hello");
    list = g_list_append(list, "GLib");
    
    // Iterate
    for (GList *l = list; l != NULL; l = l->next) {
        printf("Item: %s\n", (char *)l->data);
    }
    
    g_list_free(list);
    return 0;
}

g_list_free

void g_list_free(GList *list)

Frees all of the memory used by a GList. The freed elements are returned to the slice allocator. (Does not free the data pointers).

Strings

g_strdup

gchar *g_strdup(const gchar *str)

Duplicates a string.

Returns: A newly allocated string which matches str. usage g_free() to release it.

g_str_equal

gboolean g_str_equal(gconstpointer v1, gconstpointer v2)

Compares two strings for equality.

Returns: TRUE if the strings are the same, FALSE otherwise.

Event Loop

g_main_loop_new

GMainLoop *g_main_loop_new(GMainContext *context, gboolean is_running)

Creates a new GMainLoop structure.

Returns: A new GMainLoop.

g_main_loop_run

void g_main_loop_run(GMainLoop *loop)

Runs a main loop until g_main_loop_quit() is called on the loop.

Error Handling

g_set_error

void g_set_error(GError **err, GQuark domain, gint code, const gchar *format, ...)

Sets err to a new GError created from the arguments.