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Date: Thu, 29 Sep 2011 22:23:58 +0200
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To: Andrey Hristov <php@hristov.com>
CC: Gustavo Lopes <glopes@nebm.ist.utl.pt>, internals@lists.php.net
References: <CAD83JAVvBQ-zjR2Fnmf1MQwf_Rh+OQjqWsjUeNqB4WTjxf-TOw@mail.gmail.com> <4E848B31.2030501@gmail.com> <CAD83JAU_TOf2YimY_2C1DarFFDkfLFWoZrUZaMixOtBDa-8yUg@mail.gmail.com> <4E84A73E.8030601@gmail.com> <4E84B4DE.3070904@hristov.com>
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Subject: Re: [PHP-DEV] Cast trap with INI entries compiling C++ extension
From: keisial@gmail.com ("=?UTF-8?B?w4FuZ2VsIEdvbnrDoWxleg==?=")

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Gustavo Lopes wrote:
> const char * and char const * are the same (just like const int and 
> int const are the same); what's not the same is char *const. 

Andrey Hristov wrote:
> it's easy, whatever const is closer to is immutable
> const char * is a pointer to a const char, because the const is closer 
> to the char than to the pointer.
> char * const is a const pointer to a char, because the const is closer 
> to the pointer than to the char.
> Anyway, never used char const *, which will conflict with my 
> explanation :)
>
> Best,
> Andrey


I stand corrected, char const * is the same as const char* [1], so any 
of them would
work for the ini struct.
The C++ FAQ Lite recommends reading it right to left [2], but then the 
leftmost const
case is left undefined by the mnemonic, so it isn't valid for all cases, 
either.

I'm also attaching a small program showing the different ways of 
accessing each of those
and the expected warnings so that your favorite compiler can yell at you :)


[1] http://www.parashift.com/c++-faq/const-correctness.html#faq-18.9
[2] http://www.parashift.com/c++-faq/const-correctness.html#faq-18.5



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int main() {
	const char* char_const1 = "ABC";
	char_const1[0] = 'B'; /* Error */
	char_const1 = "DEF"; /* Ok */
	
	char const* char_const2 = "ABC";
	char_const2[0] = 'B'; /* Error */
	char_const2 = "DEF"; /* Ok */
	
	char * const ptr_const = "ABC";
	ptr_const[0] = 'B'; /* Ok */
	ptr_const = "DEF"; /* Error */
	
	char const * const const_const = "ABC";
	const_const[0] = 'B'; /* Error */
	const_const = "DEF"; /* Error */
	
	return 0;
}

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