Name
	n3620, alx-0028r2 - add st*rspn(), st*rcspn(), wc*rspn(), wc*rcspn()

Principles
	-  Codify existing practice to address evident deficiencies.
	-  Enable secure programming

Category
	Standardize common string APIs

Author
	Alejandro Colomar <alx@kernel.org>

History
	<https://www.alejandro-colomar.es/src/alx/alx/wg14/alx-0028.git/>

	r0 (2025-06-14):
	-  Initial draft.

	r1 (2025-06-26):
	-  tfix.
	-  s/Description/Rationale/

	r2 (2025-06-27; n3620):
	-  wfix.

Rationale
	Searching for a span starting at the end of a string is a common
	operation.  It allows easily removing trailing withe space in a
	line, for example:

		stpcpy(stprspn(buf, " \t\n"), "");

	A variant that searches for the complementary span, stprcspn()
	is interesting for example for finding the basename of a path:

		stprcspn(s, "/");

Prior art
	Solaris provides strrspn(3GEN), although it returns a pointer.
	This is inconsistent with the existing strspn(3) family of
	functions, which returns an offset.

Design decisions
	For returning a pointer, a better name for the Solaris API would
	have been stprspn().  Let's add it here as stprspn(), and turn
	Solaris into non-conforming in this regard.

Proposed wording
	Based on N3550.

    7.28.5.1
	Add 'stprcspn' and 'stprspn' in the first sentence.

    7.28.5  String handling <string.h> :: Search functions
	## New sections after 7.28.5.4 ("The strcspn function")

	+7.28.5.4+1  The <b>strrcspn</b> function
	+
	+Synopsis
	+1	#include <string.h>
	+	size_t strrcspn(const char *s, const char *reject);
	+
	+Description
	+2	The <b>strrcspn</b> function
	+	computes the offset of the maximum final segment
	+	of the string pointed to by <tt>s</tt>
	+	which consists entirely of
	+	characters <i>not</i> from
	+	the string poined to by <tt>reject</tt>.
	+
	+Returns
	+3	The <b>strrcspn</b> function returns
	+	the offset of the segment
	+	from the begining of the string pointed to by <tt>s</tt>.
	+
	+7.28.5.4+2  The <b>stprcspn</b> generic function
	+
	+Synopsis
	+1	#include <string.h>
	+	QChar *stprcspn(QChar *s, const char *reject);
	+
	+Description
	+2	The <b>stprcspn</b> generic function
	+	is equivalent to <b>strrcspn</b>,
	+	except for the return value.
	+
	+Returns
	+3	The <b>stprcspn</b> generic function returns
	+	<tt>s + strrcspn(s, reject)</tt>

	## New sections after 7.28.5.7 ("The strspn function")

	+7.28.5.7+1  The <b>strrspn</b> function
	+
	+Synopsis
	+1	#include <string.h>
	+	size_t strrspn(const char *s, const char *accept);
	+
	+Description
	+2	The <b>strrspn</b> function
	+	computes the offset of the maximum final segment
	+	of the string pointed to by <tt>s</tt>
	+	which consists entirely of
	+	characters from
	+	the string poined to by <tt>accept</tt>.
	+
	+Returns
	+3	The <b>strrspn</b> function returns
	+	the offset of the segment
	+	from the begining of the string pointed to by <tt>s</tt>.
	+
	+7.28.5.4+2  The <b>stprspn</b> generic function
	+
	+Synopsis
	+1	#include <string.h>
	+	QChar *stprspn(QChar *s, const char *accept);
	+
	+Description
	+2	The <b>stprspn</b> generic function
	+	is equivalent to <b>strrspn</b>,
	+	except for the return value.
	+
	+Returns
	+3	The <b>stprspn</b> generic function returns
	+	<tt>s + strrspn(s, acccept)</tt>

    7.28.5.1
	Add 'wcprcspn' and 'wcprspn' in the first sentence.

    7.33.4.6  General wide string utilities :: Wide string search functions
	## New sections after 7.33.4.6.3 ("The wcscspn function")

	+7.33.4.6.3+1  The <b>wcsrcspn</b> function
	+
	+Synopsis
	+1	#include <wchar.h>
	+	size_t wcsrcspn(const wchar_t *s, const wchar_t *reject);
	+
	+Description
	+2	The <b>wcsrcspn</b> function
	+	is equivalent to <b>strrcspn</b>
	+	except that it handles wide strings.
	+
	+7.33.4.6.3+2  The <b>wcprcspn</b> generic function
	+
	+Synopsis
	+1	#include <wchar.h>
	+	QWchar *wcprcspn(QWchar *p, const wchar_t *reject);
	+
	+Description
	+2	The <b>wcprcspn</b> generic function
	+	is equivalent to <b>stprcspn</b>
	+	except that it handles wide strings.

	## New sections after 7.33.4.6.6 ("The wcsspn function")

	+7.33.4.6.6+1  The <b>wcsrspn</b> function
	+
	+Synopsis
	+1	#include <wchar.h>
	+	size_t wcsrspn(const wchar_t *s, const wchar_t *accept);
	+
	+Description
	+2	The <b>wcsrspn</b> function
	+	is equivalent to <b>strrspn</b>
	+	except that it handles wide strings.
	+
	+7.33.4.6.6+2  The <b>wcprspn</b> generic function
	+
	+Synopsis
	+1	#include <wchar.h>
	+	QWchar *wcprspn(QWchar *p, const wchar_t *acccept);
	+
	+Description
	+2	The <b>wcprspn</b> generic function
	+	is equivalent to <b>stprspn</b>
	+	except that it handles wide strings.

    7.35.18  String handling <string.h>
	Add 'stprcspn' and 'stprspn' in the second paragraph.

    7.35.21  Extended multibyte and wide character utilities <wchar.h>
	Add 'wcprcspn' and 'wcprspn' in the third paragraph.