声明gchar后是否需调用g_free？GTK+树视图过滤器内存疑问

Hey there! As someone starting out with GTK+ and C, navigating GLib's memory management can feel a bit tricky at first—let's unpack your questions clearly.

Why is g_free() being called in your code? #

First, let's recap the core rule: GLib's memory allocation functions (like g_malloc(), g_new(), g_strdup(), etc.) pair exclusively with g_free(), just like standard C's malloc() pairs with free(). GLib uses its own memory pooling system under the hood, so mixing allocators and deallocators (like using free() on memory from g_malloc()) will lead to undefined behavior.

In the context of a GtkTreeView filter, you're probably using GLib functions to allocate temporary data in your filter callback. For example:

• If you're extracting a string from the tree model and duplicating it with g_strdup() to perform a match, that duplicated string lives in heap memory managed by GLib.
• If you're dynamically allocating a buffer with g_malloc() to hold processed data for filtering.

In these cases, calling g_free() is mandatory to avoid memory leaks. The filter callback runs every time the view updates, so leaking memory here would add up quickly!

Do you need to call g_free() on a declared gchar? #

This depends entirely on how the gchar (or gchar*) was allocated:

• Stack-allocated gchar arrays: If you declare something like gchar buffer[128]; or gchar *static_str = "fixed string";, this memory lives on the stack or in the program's read-only data segment. You never need to call g_free() (or free()) on these—they're automatically cleaned up when they go out of scope.
• Dynamically allocated via GLib: If you used g_strdup(), g_malloc(), g_new(gchar, ...), or any other GLib function that explicitly allocates heap memory, you must call g_free() to release that memory when you're done with it.
• Dynamically allocated via standard C: If you used malloc() or calloc() for a gchar*, stick with standard free() instead of g_free().

A quick pro tip for GTK+ development: Always check the documentation for functions that return strings or objects. Many GTK+ functions will return data that's already owned by a widget or container—meaning you don't need to free it yourself. For example, if you use gtk_tree_model_get() to fetch a string from a tree row, the documentation will tell you whether you need to call g_free() on the result.

内容的提问来源于stack exchange，提问作者sprocket12