为__attribute __支持自定义（（格式）） [英] Custom support for __attribute__((format))

问题描述

GCC和锵两者都有支持，使对可变参数的功能，如的printf 编译时检查。这些编译器接受的语法如下：

Both GCC and Clang have a support to make compile-time checks on variable argument functions like printf. These compilers accept syntax like:

extern void dprintf(int dlevel, const char *format, ...)
  __attribute__((format(printf, 2, 3)));  /* 2=format 3=params */

在OSX中，Cocoa框架也使用了这样的一个扩展的NSString ：

On OSX, the Cocoa framework also use an extension of this for NSString:

#define NS_FORMAT_FUNCTION(F,A) __attribute__((format(__NSString__, F, A)))

在我们公司，我们有像一堆类即basestring 自定义的C ++框架从 BaseObject 所有派生。在即basestring 有几个可变参数的方法类似于的sprintf ，但也有一些扩展。例如，％S预计类型的参数即basestring * 和％ @需要一个 BaseObject * 参数。

In our company, we have a custom C++ framework with a bunch of classes like BaseString all deriving from BaseObject. In BaseString there are a few variable argument methods similar to sprintf, but with some extensions. For example, "%S" expects an argument of type BaseString*, and "%@" expects a BaseObject* argument.

我想执行的在我们的项目参数的编译时检查，但由于扩展， __属性__（（格式（printf的）））给很多假阳性警告。

I would like to perform a compile-time check of the arguments in our projects, but because of the extensions, __attribute__((format(printf))) give lots of false positive warnings.

有没有一种方法来定制 __ __属性的支持（（格式））两个编译器中的一个？如果需要修补程序编译器源代码，它是可行的在一个合理的时间？另外，是否有其他的皮棉的喜欢，可以执行检查工具？

Is there a way to customize the support of __attribute__((format)) for one of the two compilers ? If this requires a patch to the compiler source, is it doable in a reasonable amount of time ? Alternatively, are there other lint like tools that could perform the check ?

推荐答案

问了这个问题，一年半后，我想出了一个完全不同的方法来解决真正的问题：有什么办法静态检查类型的自定义可变参数的格式化报表？的

One year and a half after having asked this question, I came out with a totally different approach to solve the real problem: Is there any way to statically check the types of custom variadic formatting statements?

有关完整，因为它可以帮助其他人，这里是解决方案，我终于实现。它拥有超过原来的问题有两个好处：

For completeness and because it can help other people, here is the solution I have finally implemented. It has two advantages over the original question:

• 比较简单：在不到一天的时间来实现;


• 编译器独立：可以检查C ++ code任何平台（Windows，Android的，OSX，...）上

一个Perl脚本解析源$ C ​​$ C，认定该格式字符串和德codeS里面他们百分之修饰。然后，将全部的论点为模板的身份函数的调用 CheckFormat＆LT;＆GT; 。例如：

A Perl script parses the source code, finds the formatting strings and decodes the percent modifiers inside them. It then wraps all arguments with a call to a template identity function CheckFormat<>. Example:

str->appendFormat("%hhu items (%.2f %%) from %S processed", 
    nbItems, 
    nbItems * 100. / totalItems, 
    subject);

变成了：

str->appendFormat("%hhu items (%.2f %%) from %S processed", 
    CheckFormat<CFL::u, CFM::hh>(nbItems  ), 
    CheckFormat<CFL::f, CFM::_>(nbItems * 100. / totalItems  ), 
    CheckFormat<CFL::S, CFM::_, const BaseString*>(subject  ));

该枚举 CFL ， CFM 和模板函数 CheckFormat 必须在这样的公共头文件中定义（这是一个提取物，大约有24重载）。

The enumerations CFL, CFM and the template function CheckFormat must be defined in a common header file like this (this is an extract, there are around 24 overloads).

enum class CFL
{
    c, d, i=d, star=i, u, o=u, x=u, X=u, f, F=f, e=f, E=f, g=f, G=f, p, s, S, P=S, at
};
enum class CFM
{
    hh, h, l, z, ll, L=ll, _
};
template<CFL letter, CFM modifier, typename T> inline T CheckFormat(T value) { CFL test= value; (void)test; return value; }
template<> inline const BaseString* CheckFormat<CFL::S, CFM::_, const BaseString*>(const BaseString* value) { return value; }
template<> inline const BaseObject* CheckFormat<CFL::at, CFM::_, const BaseObject*>(const BaseObject* value) { return value; }
template<> inline const char* CheckFormat<CFL::s, CFM::_, const char*>(const char* value) { return value; }
template<> inline const void* CheckFormat<CFL::p, CFM::_, const void*>(const void* value) { return value; }
template<> inline char CheckFormat<CFL::c, CFM::_, char>(char value) { return value; }
template<> inline double CheckFormat<CFL::f, CFM::_, double>(double value) { return value; }
template<> inline float CheckFormat<CFL::f, CFM::_, float>(float value) { return value; }
template<> inline int CheckFormat<CFL::d, CFM::_, int>(int value) { return value; }

...

具有编译错误后，很容易用常规的前pression恢复原来的形式 CheckFormat＆LT; [^＆LT;] *＆GT; \\（？（*）\\） 其捕获取代。

这篇关于为__attribute __支持自定义（（格式））的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！