T const & が char[]を受け取れない / T const & cannot receive char[]

T const & が char[]を受け取れない / T const & cannot receive char[] by はぴぴ

Closed

as Fixed

Type:	Bug
ID:	724314
Opened:	2/9/2012 6:37:23 PM
Access Restriction:	Public

Workaround(s)

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User(s) can reproduce this bug

Visual C++ 2010 Expressを使用しています。
I use Visual C++ 2010 Express.

どのような引数の参照でも受け取れる関数 template<typename T> f(T const &) を作ろうとしていた所、サイズが0または未定の配列である、char [] 型の変数を受け取れないことがわかりました。
When I make a function "template<typename T> f(T const &)" which can recieve any reference of argument, I notice it cannot recieve a variable of 0 size array / pending size array - char [].

char [] が char * に暗黙にキャストされ、char * が char *const & に暗黙にキャストされて f(T const &) に渡されると意図しました。
I intend to convert char [] to char * implicitly, and to convert char * to char *const & implicitly.

しかし、なぜか、char [] は char const (&)[1] への変換が試みられたようです。
But, char [] was tried to convert char const (&)[1] somehow.

char *const & または char const (&)[] のどちらかに暗黙に変換されるべきではないでしょうか?
Should it be converted to char *const & or char const (&)[]?

Details (expand)

Visual Studio 2010 SP1

extern char a[];
struct A{
char a[];
} d;

char *b = "b";
char c[] = "c";

template<typename T>
void f(T const &){}

int main(int argc, char *argv[]){

//1 番目の引数を 'char []' から 'char const (&)[1]' に変換できません
//cannot convert 1st argument from char [] to char const (&)[1]
f(a); //C2664
f(d.a); //C2664

f(b); //ok
f(c); //ok
f(argv[0]); //ok: argv[0] is not char [] but char*

}

char a[] = "a";

Japanese

Windows XP

Japanese

C2664: 1 番目の引数を 'char []' から 'char const (&)[1]' に変換できません
C2664: cannot convert 1st argument from char [] to char const (&)[1]

char [] が char *const & または char const (&)[] に暗黙に変換される
char [] is converted to char *const or char const (&)[] implicitly

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[Problem Description]:
I use Visual C++ 2010 Express. While I attempted to make function template f(T const &) that can receive reference of any argument, I found that it cannot receive variables of char [] type, which has size of 0 or unscheduled arrangement. I intended char [] to be tacitly converted to char * and then char * to be tacitly converted to char *const & and then passed to f(T const &). However, somehow it seems that an attempt was made to convert char [] to char const (&)[1]. Shouldn't it be converted to either char *const & or char const (&)[] tacitly?

[Repro Steps:]
extern char a[];
struct A{
char a[];
} d;
char *b = "b";
char c[] = "c";
template<typename T>
void f(T const &){}
int main(int argc, char *argv[]){
// cannot convert 1st argument from 'char []' to 'char const (&)[1]'
//cannot convert 1st argument from char [] to char const (&)[1]
f(a); //C2664
f(d.a); //C2664
f(b); //ok
f(c); //ok
f(argv[0]); //ok: argv[0] is not char [] but char*
}
char a[] = "a";
[Actual Results]:
C2664: Cannot convert 1st argument from 'char []' to 'char const (&)[1].'

[Expected Results]:
char [' converted to char *const & or char const (&)[] tacitly.

C2664: Cannot convert 1st argument from 'char []' to 'char const (&)[1]'
char [] converted to char const & or char const (&)[] tacitly.