BREAKING CHANGE: change mark_count to do what's documented (and what the std does).

See https://svn.boost.org/trac/boost/ticket/9227.

include/boost/regex/v4/basic_regex.hpp

@@ -236,9 +236,7 @@ public:
    }
    std::pair<const_iterator, const_iterator> BOOST_REGEX_CALL subexpression(std::size_t n)const
    {
-      if(n == 0)
+      const std::pair<std::size_t, std::size_t>& pi = this->m_subs.at(n);
-         boost::throw_exception(std::out_of_range("0 is not a valid subexpression index."));
-      const std::pair<std::size_t, std::size_t>& pi = this->m_subs.at(n - 1);
       std::pair<const_iterator, const_iterator> p(expression() + pi.first, expression() + pi.second);
       return p;
    }
@@ -266,7 +264,7 @@ public:
    }
    size_type BOOST_REGEX_CALL mark_count()const
    {
-      return this->m_mark_count;
+      return this->m_mark_count - 1;
    }
    const re_detail::re_syntax_base* get_first_state()const
    {

include/boost/regex/v4/perl_matcher_common.hpp

@@ -200,7 +200,7 @@ bool perl_matcher<BidiIterator, Allocator, traits>::match_imp()
    search_base = base;
    state_count = 0;
    m_match_flags |= regex_constants::match_all;
-   m_presult->set_size((m_match_flags & match_nosubs) ? 1 : re.mark_count(), search_base, last);
+   m_presult->set_size((m_match_flags & match_nosubs) ? 1 : 1 + re.mark_count(), search_base, last);
    m_presult->set_base(base);
    m_presult->set_named_subs(this->re.get_named_subs());
    if(m_match_flags & match_posix)
@@ -262,7 +262,7 @@ bool perl_matcher<BidiIterator, Allocator, traits>::find_imp()
       // reset our state machine:
       search_base = position = base;
       pstate = re.get_first_state();
-      m_presult->set_size((m_match_flags & match_nosubs) ? 1 : re.mark_count(), base, last);
+      m_presult->set_size((m_match_flags & match_nosubs) ? 1 : 1 + re.mark_count(), base, last);
       m_presult->set_base(base);
       m_presult->set_named_subs(this->re.get_named_subs());
       m_match_flags |= regex_constants::match_init;
@@ -281,13 +281,13 @@ bool perl_matcher<BidiIterator, Allocator, traits>::find_imp()
             ++position;
       }
       // reset $` start:
-      m_presult->set_size((m_match_flags & match_nosubs) ? 1 : re.mark_count(), search_base, last);
+      m_presult->set_size((m_match_flags & match_nosubs) ? 1 : 1 + re.mark_count(), search_base, last);
       //if((base != search_base) && (base == backstop))
       //   m_match_flags |= match_prev_avail;
    }
    if(m_match_flags & match_posix)
    {
-      m_result.set_size(re.mark_count(), base, last);
+      m_result.set_size(1 + re.mark_count(), base, last);
       m_result.set_base(base);
    }
 

include/boost/regex/v4/regex_split.hpp

@@ -119,7 +119,7 @@ std::size_t regex_split(OutputIterator out,
    // if there is still input left, do a final push as long as max_split
    // is not exhausted, and we're not splitting sub-expressions rather 
    // than whitespace:
-   if(max_split && (last != s.end()) && (e.mark_count() == 1))
+   if(max_split && (last != s.end()) && (e.mark_count() == 0))
    {
       *out = std::basic_string<charT, Traits1, Alloc1>((ci_t)last, (ci_t)s.end());
       ++out;

src/posix_api.cpp

@@ -125,7 +125,7 @@ BOOST_REGEX_DECL int BOOST_REGEX_CCALL regcompA(regex_tA* expression, const char
 #endif
       expression->re_magic = magic_value;
       static_cast<c_regex_type*>(expression->guts)->set_expression(ptr, p2, flags);
-      expression->re_nsub = static_cast<c_regex_type*>(expression->guts)->mark_count() - 1;
+      expression->re_nsub = static_cast<c_regex_type*>(expression->guts)->mark_count();
       result = static_cast<c_regex_type*>(expression->guts)->error_code();
 #ifndef BOOST_NO_EXCEPTIONS
    } 

src/wide_posix_api.cpp

@@ -135,7 +135,7 @@ BOOST_REGEX_DECL int BOOST_REGEX_CCALL regcompW(regex_tW* expression, const wcha
 #endif
       expression->re_magic = wmagic_value;
       static_cast<wc_regex_type*>(expression->guts)->set_expression(ptr, p2, flags);
-      expression->re_nsub = static_cast<wc_regex_type*>(expression->guts)->mark_count() - 1;
+      expression->re_nsub = static_cast<wc_regex_type*>(expression->guts)->mark_count();
       result = static_cast<wc_regex_type*>(expression->guts)->error_code();
 #ifndef BOOST_NO_EXCEPTIONS
    } 

test/regress/test_regex_search.hpp

@@ -511,7 +511,7 @@ void test(boost::basic_regex<charT, traits>& r, const test_regex_search_tag&)
          }
       }
       r.assign(expression, syntax_options | boost::regbase::save_subexpression_location);
-      for(std::size_t i = 1; i < r.mark_count(); ++i)
+      for(std::size_t i = 0; i < r.mark_count(); ++i)
       {
          std::pair<const charT*, const charT*> p = r.subexpression(i);
          if(*p.first != '(')