迭代器不属于其分配的文本缓冲区

这是一个简单的骨头save_as()功能：

gint save_as(GtkWidget *parent, struct buffers B)
{
    GtkWidget *file_chooser = gtk_file_chooser_dialog_new("Save As", GTK_WINDOW(parent), GTK_FILE_CHOOSER_ACTION_SAVE, "Cancel", GTK_RESPONSE_CANCEL, "Save", GTK_RESPONSE_OK, NULL);
    gtk_file_chooser_set_current_name(GTK_FILE_CHOOSER(file_chooser), "Untitled");

    gint response = gtk_dialog_run(GTK_DIALOG(file_chooser));
    switch(response)
    {
        case GTK_RESPONSE_OK:
                GFile *file = g_file_new_for_path(gtk_file_chooser_get_filename(GTK_FILE_CHOOSER(file_chooser)));
                GtkTextIter *start;
                gtk_text_buffer_get_start(B.buffer0, &start);
                GtkTextIter *end;
                gtk_text_buffer_get_end(B.buffer0, &end);
                // program abnormally terminates on the following line
                gchar *contents = gtk_text_buffer_get_text(B.buffer0, &start, &end, FALSE);
                g_file_replace_contents(file, contents, strlen(contents), NULL, FALSE, G_FILE_CREATE_NONE, NULL, NULL, NULL);
                g_free(contents);
                gtk_widget_destroy(file_chooser);
                return GTK_RESPONSE_OK;
                break;
        case GTK_RESPONSE_CANCEL:
                gtk_widget_destroy(file_chooser);
                return GTK_RESPONSE_CANCEL;
    }
    // user pressed X
    gtk_widget_destroy(file_chooser);
    return GTK_RESPONSE_CANCEL;
}

这几乎就是我们诊断和解决问题所需的全部内容。

这是我尝试单击时收到的完整消息文件 -> 另存为...然后继续Save:

(test:4478): Gtk-WARNING **: 11:56:20.184: Invalid text buffer iterator: either the iterator is uninitialized, or the characters/pixbufs/widgets in the buffer have been modified since the iterator was created.
You must use marks, character numbers, or line numbers to preserve a position across buffer modifications.
You can apply tags and insert marks without invalidating your iterators, but any mutation that affects 'indexable' buffer contents (contents that can be referred to by character offset) will invalidate all outstanding iterators


(test:4478): Gtk-CRITICAL **: 11:56:20.184: gtk_text_buffer_get_text: assertion 'gtk_text_iter_get_buffer (start) == buffer' failed
Segmentation fault (core dumped)

由于某种原因，迭代器似乎start and end不属于B.buffer0。除了GTK+3 文档 https://developer.gnome.org/gtk3/stable/，我也关注了答案这个问题 https://stackoverflow.com/questions/11088338/how-to-save-content-of-gtktextbuffer-to-a-file作为指导。

为什么会发生这种情况以及如何解决？

---

I also tried changing the following lines:

gtk_text_buffer_get_start_iter(B.buffer0, &start); to gtk_text_buffer_get_start_iter(B.buffer0, start);

gtk_text_buffer_get_start_iter(B.buffer0, &end); to gtk_text_buffer_get_start_iter(B.buffer0, end);

gchar *contents = gtk_text_buffer_get_text(B.buffer0, &start, &end, FALSE); to gchar *contents = gtk_text_buffer_get_text(B.buffer0, start, end, FALSE);

我得到的唯一错误是：

Segmentation fault (core dumped)

这也应该是根据以下内容发送参数的正确方法文档 https://developer.gnome.org/gtk3/stable/GtkTextBuffer.html.

另外，我尝试更换contents = gtk_text_buffer_get_text(B.buffer0, start, end, FALSE); with contents = gtk_text_iter_get_text(start, end);但我得到同样的错误。

我还注意到，应用这些更改后，我在编译过程中收到两个警告：

src/save.c:96:5: warning: ‘start’ may be used uninitialized in this function [-Wmaybe-uninitialized]
     gtk_text_buffer_get_start_iter(B.buffer0, start);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/save.c:98:5: warning: ‘end’ may be used uninitialized in this function [-Wmaybe-uninitialized]
     gtk_text_buffer_get_end_iter(B.buffer0, end);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

这显然意味着gtk_text_buffer_get_start/end_iter()关联失败start and end with B.buffer0， 但为什么？它说start and end未初始化就传递了，但这不是正常的吗，因为我现在正在初始化它们？或者我应该在那之前做点什么？

---

Definition of struct buffer is in a file called buffer.h. Here it is (not the whole file, just the struct definition):

struct buffers
{
    GtkTextBuffer *buffer0;
    GtkTextBuffer *buffer1;
    GtkTextBuffer *buffer2;
};

我使用的实例是：

struct buffers Buffer;

这是一个全局变量，所以buffer.h包含在每个使用的文件中Buffer。并且出于相同的目的（全局性），当然声明extern struct buffers Buffer;在与定义它的源文件关联的头文件中。

该缓冲区被传递给一个函数save_as()像这样：

gint response = save_as(main_window, Buffer);

如果您想知道为什么我不使用全局变量而不是将其作为参数传递，这是因为我可以传递任何类型的变量struct buffers to a save_file()并让它完成工作，而不是为每个功能提供另一个功能struct buffers多变的。

---

I tried initializing iterators upon their definition:

GtkTextIter *start = NULL;
GtkTextIter *end = NULL;

一切都会编译，没有任何警告。不幸的是，这并不能解决问题。点击后文件 -> 另存为进而Save，程序退出，我收到消息：

(test:4081): Gtk-CRITICAL **: 19:48:29.843: gtk_text_buffer_get_start_iter: assertion 'iter != NULL' failed

(test:4081): Gtk-CRITICAL **: 19:48:29.844: gtk_text_buffer_get_end_iter: assertion 'iter != NULL' failed

(test:4081): Gtk-CRITICAL **: 19:48:29.844: gtk_text_buffer_get_text: assertion 'start != NULL' failed

为什么我的start and end迭代器是NULL至少在前两种情况下？这两个函数不是应该设置吗start and end分别到文件开头和结尾的迭代器？因此，为什么在此之前设置的迭代器很重要？

终于解决了。看起来像那样GtkTextIter与大多数 GTK 类型略有不同。

这是应该如何完成的：

gint save_as(GtkWidget *parent, struct buffers B)
{
    GtkWidget *file_chooser = gtk_file_chooser_dialog_new("Save As", GTK_WINDOW(parent), GTK_FILE_CHOOSER_ACTION_SAVE, "Cancel", GTK_RESPONSE_CANCEL, "Save", GTK_RESPONSE_OK, NULL);
    gtk_file_chooser_set_current_name(GTK_FILE_CHOOSER(file_chooser), "Untitled");

    gint response = gtk_dialog_run(GTK_DIALOG(file_chooser));
    switch(response)
    {
        case GTK_RESPONSE_OK:
                GFile *file = g_file_new_for_path(gtk_file_chooser_get_filename(GTK_FILE_CHOOSER(file_chooser)));
                GtkTextIter start;
                gtk_text_buffer_get_start(B.buffer0, &start);
                GtkTextIter end;
                gtk_text_buffer_get_end(B.buffer0, &end);
                // program abnormally terminates on the following line
                gchar *contents = gtk_text_buffer_get_text(B.buffer0, &start, &end, FALSE);
                g_file_replace_contents(file, contents, strlen(contents), NULL, FALSE, G_FILE_CREATE_NONE, NULL, NULL, NULL);
                g_free(contents);
                gtk_widget_destroy(file_chooser);
                return GTK_RESPONSE_OK;
                break;
        case GTK_RESPONSE_CANCEL:
                gtk_widget_destroy(file_chooser);
                return GTK_RESPONSE_CANCEL;
    }
    // user pressed X
    gtk_widget_destroy(file_chooser);
    return GTK_RESPONSE_CANCEL;
}

如您所见，此代码与我的问题中的代码的唯一区别是以下两行：

Wrong

GtkTextIter *start;
GtkTextIter *end;

Right

GtkTextIter start;
GtkTextIter end;

大多数 GTK 类型都希望您将它们设为指针，但这个是一个例外。