编译器类型转换警告和错误

Question

if(xmlStrEquals(cur->name, (const xmlChar *) "check")) // Find out which type it is
    gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON (gtk_builder_get_object (builder, xmlGetProp(cur,"name"))),(gboolean) xmlGetProp(cur,"value"));

else if(xmlStrEquals(cur->name, (const xmlChar *) "spin"))
    gtk_adjustment_set_value(GTK_ADJUSTMENT (gtk_builder_get_object (builder, xmlGetProp(cur,"name"))),(gdouble) xmlGetProp(cur,"value"));

else if(xmlStrEquals(cur->name, (const xmlChar *) "combo"))
    gtk_combo_box_set_active(GTK_COMBO_BOX (gtk_builder_get_object (builder, xmlGetProp(cur,"name"))),(gint) xmlGetProp(cur,"value"));

下面的 3 个错误对应上面的 3 个 if 语句。

main.c:125: warning: cast from pointer to integer of different size
main.c:130: error: pointer value used where a floating point value was expected
main.c:139: warning: cast from pointer to integer of different size

如果您允许我提取有问题的部分：

(gboolean) xmlGetProp(cur,"value")
(gdouble) xmlGetProp(cur,"value")
(gint) xmlGetProp(cur,"value")

为什么这些类型转换会导致这些错误？我该如何修复它们？

尝试使用 (gboolean *) 等收到了来自 gtk 的警告，内容如下：

warning: passing argument 2 of ‘gtk_toggle_button_set_active’ makes integer from pointer without a cast
/usr/include/gtk-2.0/gtk/gtktogglebutton.h:82: note: expected ‘gboolean’ but argument is of type ‘gboolean *’
error: incompatible type for argument 2 of ‘gtk_adjustment_set_value’
/usr/include/gtk-2.0/gtk/gtkadjustment.h:93: note: expected ‘gdouble’ but argument is of type ‘gdouble *’
warning: passing argument 2 of ‘gtk_combo_box_set_active’ makes integer from pointer without a cast
/usr/include/gtk-2.0/gtk/gtkcombobox.h:99: note: expected ‘gint’ but argument is of type ‘gint *’

Answer 1

xmlGetProp 函数 返回一个字符串（如 xmlChar *):

搜索并获取与节点关联的属性的值这将执行实体替换。该函数在 DTD 属性声明中查找 #FIXED 或默认声明值，除非已关闭 DTD 使用。
[...]
返回：属性值，如果没有找到则返回 NULL。由调用者使用 xmlFree() 释放内存。

调用者负责将该字符串解析为所需的任何形式（浮点、整数、布尔值……）。另请注意，调用者也负责释放返回的 xmlChar * 字符串。

要解决您的问题，您需要以通常的方式将字符串转换为您需要的内容。并且不要忘记 xmlFree 返回的字符串。

Answer 2

我像这样修复了它：

(gboolean) *xmlGetProp(cur,"value")
(gdouble) *xmlGetProp(cur,"value")
(gint) *xmlGetProp(cur,"value")

仍然不知道为什么会起作用，但我可以猜测。