[libcxx-commits] [libcxx] Revert "[libc++] Fix `regex_search` to match `$` alone with `match_default` flag" (PR #78349)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-libcxx

Author: Sanjay Marreddi (SanjayMarreddi)

<details>
<summary>Changes</summary>

The behavior of `std::regex_search` for patterns anchored both to the start and to the end of the input went wrong after merging #<!-- -->77256 . Patterns like `"^b*$"` started matching the strings such as `"a"`, which is not expected. 

Reverts the PR: #<!-- -->77256

---
Full diff: https://github.com/llvm/llvm-project/pull/78349.diff


2 Files Affected:

- (modified) libcxx/include/regex (-3) 
- (modified) libcxx/test/std/re/re.const/re.matchflag/match_not_eol.pass.cpp (-14) 


``````````diff
diff --git a/libcxx/include/regex b/libcxx/include/regex
index 0761d9de54a95cf..b575a267583b5fe 100644
--- a/libcxx/include/regex
+++ b/libcxx/include/regex
@@ -1889,9 +1889,6 @@ 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 ce00d6ee79fc85f..edeea517d2537a3 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
@@ -47,19 +47,5 @@ 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;
 }

``````````

</details>


https://github.com/llvm/llvm-project/pull/78349