<xlocinfo.h>: Reduce size of _Ctypevec, ctype<char>, ctype<wchar_t>, and ctype<unsigned short>

[SunnyWar]

_Ctypevec has some padding that can be eliminated by moving the pointers to the front. Here are the sizes before and after rearranging the members.

class _Ctypevec	size(32):
	+---
 0	| _Page
  	| <alignment member> (size=4)
 8	| _Table
16	| _Delfl
  	| <alignment member> (size=4)
24	| _LocaleName
	+---

class std::ctype<char>	size(48):	
class std::ctype<wchar_t>	size(96):
class std::ctype<unsigned short>	size(96):

///////////  After

class _Ctypevec	size(24):
	+---
 0	| _Table
 8	| _LocaleName
16	| _Page
20	| _Delfl
	+---		
class std::ctype<char>	size(40):
class std::ctype<wchar_t>	size(88):
class std::ctype<unsigned short>	size(88):

vNext note: Resolving this issue will require breaking binary compatibility. We won't be able to accept pull requests for this issue until the vNext branch is available. See #169 for more information.

[StephanTLavavej]

Relevant code:

STL/stl/inc/xlocinfo.h

Lines 64 to 69 in 2989323

	struct _Ctypevec { // stuff needed by _Tolower, etc.
	unsigned int _Page; // UINT
	const short* _Table;
	int _Delfl;
	wchar_t* _LocaleName;
	};

[SunnyWar]

I assume pull requests for this cannot happen until #169 ?

[StephanTLavavej]

That's correct. At the moment, vNext is lower priority than finishing the GitHub migration and C++20, so the branch won't be ready for a while - but it will happen.

[SunnyWar]

That's correct. At the moment, vNext is lower priority than finishing the GitHub migration and C++20, so the branch won't be ready for a while - but it will happen.

No, priority is now on C++23. History indicates this will not happen. Closing.