[libcxx-commits] [libcxx] 0804ef2 - [libc++] Fix `regex_search` to match `$` alone with `match_default` flag (#77256)

[via libcxx-commits]

Author: Sanjay Marreddi
Date: 2024-01-09T20:39:36+01:00
New Revision: 0804ef2d1539fde7f45e18e4f87d99f7019f9aae

URL: https://github.com/llvm/llvm-project/commit/0804ef2d1539fde7f45e18e4f87d99f7019f9aae
DIFF: https://github.com/llvm/llvm-project/commit/0804ef2d1539fde7f45e18e4f87d99f7019f9aae.diff

LOG: [libc++] Fix `regex_search` to match `$` alone with `match_default` flag (#77256)

Using `regex_search` with the regex_constant `match_default` and a
simple regex pattern `$` is expected to match general strings such as
_"a", "ab", "abc"..._ at `[last, last)` positions. But, the current
implementation fails to do so.

Fixes #75042

Added: 
    

Modified: 
    libcxx/include/regex
    libcxx/test/std/re/re.const/re.matchflag/match_not_eol.pass.cpp

Removed: 
    


################################################################################
diff  --git a/libcxx/include/regex b/libcxx/include/regex
index b575a267583b5f..0761d9de54a95c 100644
--- a/libcxx/include/regex
+++ b/libcxx/include/regex
@@ -1889,6 +1889,9 @@ void __r_anchor_multiline<_CharT>::__exec(__state& __s) const {
   if (__s.__current_ == __s.__last_ && !(__s.__flags_ & regex_constants::match_not_eol)) {
     __s.__do_   = __state::__accept_but_not_consume;
     __s.__node_ = this->first();
+  } else if (__s.__current_ == __s.__first_ && !(__s.__flags_ & regex_constants::match_not_eol)) {
+    __s.__do_   = __state::__accept_but_not_consume;
+    __s.__node_ = this->first();
   } else if (__multiline_ && std::__is_eol(*__s.__current_)) {
     __s.__do_   = __state::__accept_but_not_consume;
     __s.__node_ = this->first();

diff  --git a/libcxx/test/std/re/re.const/re.matchflag/match_not_eol.pass.cpp b/libcxx/test/std/re/re.const/re.matchflag/match_not_eol.pass.cpp
index edeea517d2537a..ce00d6ee79fc85 100644
--- a/libcxx/test/std/re/re.const/re.matchflag/match_not_eol.pass.cpp
+++ b/libcxx/test/std/re/re.const/re.matchflag/match_not_eol.pass.cpp
@@ -47,5 +47,19 @@ int main(int, char**)
     assert( std::regex_search(target, re, std::regex_constants::match_not_eol));
     }
 
+    {
+      std::string target = "foo";
+      std::regex re("$");
+      assert(std::regex_search(target, re));
+      assert(!std::regex_search(target, re, std::regex_constants::match_not_eol));
+    }
+
+    {
+      std::string target = "foo";
+      std::regex re("$");
+      assert(!std::regex_match(target, re));
+      assert(!std::regex_match(target, re, std::regex_constants::match_not_eol));
+    }
+
   return 0;
 }