g ++将返回的字符串文字作为const char指针，而不是const char数组 [英] g++ treats returned string literal as const char pointer not const char array

问题描述

我看到一些奇怪的行为，当从一个函数返回一个字符串字面量应该执行使用g ++（版本4.7.3）的隐式转换。任何人都可以解释为什么会有以下代码：

I'm seeing some odd behaviour when returning a string literal from a function that should perform an implicit conversion with g++ (version 4.7.3). Can anyone explain why the following code:

#include <stdio.h>

class Test
{
public:
  template <unsigned int N>
  Test(const char (&foo)[N])
  {
    printf("Template const char array constructor\n");
  }

  Test(char* foo)
  {
    printf("char* constructor\n");
  }
};

Test fn()
{
  return "foo";
}

int main()
{
  Test t("bar");
  Test u = fn();

  return 0;
}

产生结果：

Template const char array constructor
char* constructor

on g ++？令人惊讶的是，当从fn（）生成返回值时，char *构造函数优先于const char数组构造函数。不可否认，有一个警告，从字符串常量转换为'char *'

on g++? The surprising thing being that the char* constructor is chosen in preference to the const char array constructor when generating the return value from fn(). Admittedly there is a warning, "deprecated conversion from string constant to 'char*'"

更令人惊讶的是，如果你删除char *构造函数，与g ++。

Even more surprisingly if you remove the char* constructor then the code doesn't compile with g++.

它的工作原理与clang（模板构造函数使用了两次），这使我认为这是一个编译器错误，但也许它只是一个奇怪的角落C ++规范 - 任何人都可以确认？

It works as expected with clang (Template constructor used both times), which makes me think this is a compiler bug, but maybe it's just a weird corner of the C++ spec - could anyone confirm?

推荐答案

看起来这是一个bug，影响几个版本的gcc，并再次，最近一个月前对最近的版本，4.8.2。请参见 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24666

It appears that this is a bug affecting several versions of gcc which has been reported over and over again, most recently about a month ago against the most recent version, 4.8.2. See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24666

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