这个C代码是什么意思(G_GNUC_PRINTF)？

#define G_GNUC_PRINTF( format_idx,arg_idx )    
  __attribute__((__format__ (__printf__,format_idx,arg_idx)))

从gnome documentation：

Expands to the GNU C format function attribute if the compiler is gcc. This is used for declaring functions which take a variable number of arguments,with the same syntax as printf(). It allows the compiler to type-check the arguments passed to the function.

Place the attribute after the function declaration,just before the semicolon.

Parameters:

format_idx: the index of the argument corresponding to the format string (The arguments are numbered from 1)

arg_idx: the index of the first of the format arguments

例1：

static void ddict_debug(const char* fmt,2);
//                                   |    |                 |  |
// format string,format_idx = 1 ----+    |            <----+  | 
// format arguments,arg_idx = 2 ---------+            <-------+

例2：

static void foo_debug(int foo,const char* fmt,...) G_GNUC_PRINTF(2,3);
//                         |                |    |                 |  |
// not a printf argument --+                |    |                 |  |
// format string,format_idx = 2 -----------+    |            <----+  |
// format arguments,arg_idx = 3 ----------------+            <-------+

摘要：

Is there just one function declaration or two ?

一个类似printf()的函数被定义.宏告诉编译器对传递给函数的参数进行类型检查.