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Empty expressions, and empty alternatives are now

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allowed when using the Perl regular expression syntax.  This change has
been added for Perl compatibility, when the new [syntax_option_type]
['no_empty_expressions] is set then the old behaviour is preserved and
empty expressions are prohibited.  This is issue
[@https://svn.boost.org/trac/boost/ticket/1081 #1081].

Fixes #1081.

[SVN r50374]
This commit is contained in:
John Maddock
2008-12-23 19:06:04 +00:00
parent b4152cd74d
commit e4b31ea37f
25 changed files with 147 additions and 81 deletions
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25
include/boost/regex/v4/basic_regex_parser.hpp
View File

@ -109,7 +109,11 @@ void basic_regex_parser<charT, traits>::parse(const charT* p1, const charT* p2,
m_position = m_base = p1;
m_end = p2;
// empty strings are errors:
if(p1 == p2)
if((p1 == p2) &&
(
(l_flags & regbase::main_option_type) != regbase::perl_syntax_group)
|| (l_flags & regbase::no_empty_expressions)
)
{
fail(regex_constants::error_empty, 0);
return;
@ -926,7 +930,15 @@ bool basic_regex_parser<charT, traits>::parse_alt()
// error check: if there have been no previous states,
// or if the last state was a '(' then error:
//
if((this->m_last_state == 0) || (this->m_last_state->type == syntax_element_startmark))
if(
((this->m_last_state == 0) || (this->m_last_state->type == syntax_element_startmark))
&&
!(
((this->flags() & regbase::main_option_type) == regbase::perl_syntax_group)
&&
((this->flags() & regbase::no_empty_expressions) == 0)
)
)
{
fail(regex_constants::error_empty, this->m_position - this->m_base);
return false;
@ -2075,7 +2087,14 @@ bool basic_regex_parser<charT, traits>::unwind_alts(std::ptrdiff_t last_paren_st
// alternative then that's an error:
//
if((this->m_alt_insert_point == static_cast<std::ptrdiff_t>(this->m_pdata->m_data.size()))
&& m_alt_jumps.size() && (m_alt_jumps.back() > last_paren_start))
&& m_alt_jumps.size() && (m_alt_jumps.back() > last_paren_start)
&&
!(
((this->flags() & regbase::main_option_type) == regbase::perl_syntax_group)
&&
((this->flags() & regbase::no_empty_expressions) == 0)
)
)
{
fail(regex_constants::error_empty, this->m_position - this->m_base);
return false;

2
include/boost/regex/v4/regbase.hpp
View File

@ -85,6 +85,7 @@ public:
collate = 1 << 21, // use locale specific collation
nosubs = 1 << 22, // don't mark sub-expressions
save_subexpression_location = 1 << 23, // save subexpression locations
no_empty_expressions = 1 << 24, // no empty expressions allowed
optimize = 0, // not really supported
@ -143,6 +144,7 @@ namespace regex_constants{
mod_s = ::boost::regbase::mod_s,
no_mod_s = ::boost::regbase::no_mod_s,
save_subexpression_location = ::boost::regbase::save_subexpression_location,
no_empty_expressions = ::boost::regbase::no_empty_expressions,
basic = ::boost::regbase::basic,
extended = ::boost::regbase::extended,