在C ++中清除代码printf size_t（或：C ++中最接近C99的％z） [英] Clean code to printf size_t in C++ (or: Nearest equivalent of C99's %z in C++)

问题描述

我有一些打印 size_t 的C ++代码：

  size_t a; 
 printf（％lu，a）; 
  

我想在32位和64位架构上编译时不会出现警告。 p>

如果这是C99，我可以使用 printf（％z，a）; 。但是在任何标准C ++方言中不存在AFAICT ％z 。因此，我必须做

  printf（％lu，（unsigned long）a）; 
  

这真是丑陋。

没有工具打印<​​code> size_t s内置的语言，我想知道是否可能写一个printf包装器或一些，将插入适当的铸造在 size_t ，以便消除伪编译器警告，同时仍然保持良好的编译器警告。

任何想法？

---

编辑要澄清为什么我使用printf：我有一个相对较大的代码库，我正在清理。它使用printf包装器来执行写警告，将其记录到文件，并且可能退出代码并报错等事情。我可能能够提出足够的C ++ - foo来做这个cout包装，但我不想改变每个warn（）调用程序只是为了摆脱一些编译器警告。

解决方案

大多数编译器都有自己的说明符 size_t 和 ptrdiff_t 参数，Visual C ++例如分别使用％Iu和％Id，我认为gcc将允许您使用％zu和％zd。

创建一个宏：

  #if defined（_MSC_VER）||定义（__ MINGW32__）// __ MINGW32__应该__GNUC__ 
的#define JL_SIZE_T_SPECIFIER前行的Iu％
的#define JL_SSIZE_T_SPECIFIER％ID
的#define JL_PTRDIFF_T_SPECIFIER％ID
 #elif指令定义（__ GNUC__）
的#define JL_SIZE_T_SPECIFIER％俎
的#define JL_SSIZE_T_SPECIFIERZD％
的#define JL_PTRDIFF_T_SPECIFIERZD％
的#else 
 // TODO找出哪些使用。 
＃如果NUMBITS == 32 
的#define JL_SIZE_T_SPECIFIER something_unsigned 
的#define JL_SSIZE_T_SPECIFIER something_signed 
的#define JL_PTRDIFF_T_SPECIFIER something_signed 
的#else 
的#define JL_SIZE_T_SPECIFIER something_bigger_unsigned 
的#define JL_SSIZE_T_SPECIFIER something_bigger_signed 
的#define JL_PTRDIFF_T_SPECIFIER东西，bigger_signed 
 #ENDIF 
 #ENDIF 
  

用法：

 为size_t一个; 
的printf（JL_SIZE_T_SPECIFIER，A）; 
的printf（下的大小是JL_SIZE_T_SPECIFIER字节，一）; 
  

I have some C++ code that prints a size_t:

size_t a;
printf("%lu", a);

I'd like this to compile without warnings on both 32- and 64-bit architectures.

If this were C99, I could use printf("%z", a);. But AFAICT %z doesn't exist in any standard C++ dialect. So instead, I have to do

printf("%lu", (unsigned long) a);

which is really ugly.

If there's no facility for printing size_ts built into the language, I wonder if it's possible to write a printf wrapper or somesuch such that will insert the appropriate casts on size_ts so as to eliminate spurious compiler warnings while still maintaining the good ones.

Any ideas?

---

Edit To clarify why I'm using printf: I have a relatively large code base that I'm cleaning up. It uses printf wrappers to do things like "write a warning, log it to a file, and possibly exit the code with an error". I might be able to muster up enough C++-foo to do this with a cout wrapper, but I'd rather not change every warn() call in the program just to get rid of some compiler warnings.

解决方案

Most compilers have their own specifier for size_t and ptrdiff_t arguments, Visual C++ for instance use %Iu and %Id respectively, I think that gcc will allow you to use %zu and %zd.

You could create a macro:

#if defined(_MSC_VER) || defined(__MINGW32__) //__MINGW32__ should goes before __GNUC__
  #define JL_SIZE_T_SPECIFIER    "%Iu"
  #define JL_SSIZE_T_SPECIFIER   "%Id"
  #define JL_PTRDIFF_T_SPECIFIER "%Id"
#elif defined(__GNUC__)
  #define JL_SIZE_T_SPECIFIER    "%zu"
  #define JL_SSIZE_T_SPECIFIER   "%zd"
  #define JL_PTRDIFF_T_SPECIFIER "%zd"
#else
  // TODO figure out which to use.
  #if NUMBITS == 32
    #define JL_SIZE_T_SPECIFIER    something_unsigned
    #define JL_SSIZE_T_SPECIFIER   something_signed
    #define JL_PTRDIFF_T_SPECIFIER something_signed
  #else
    #define JL_SIZE_T_SPECIFIER    something_bigger_unsigned
    #define JL_SSIZE_T_SPECIFIER   something_bigger_signed
    #define JL_PTRDIFF_T_SPECIFIER something-bigger_signed
  #endif
#endif

Usage:

size_t a;
printf(JL_SIZE_T_SPECIFIER, a);
printf("The size of a is " JL_SIZE_T_SPECIFIER " bytes", a);

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