[libc++][regex] Fix #51028 throw exception in the case of wrong range

Author: alexey.lazarev

libcxx/include/__cxx03/regex

@@ -2100,7 +2100,7 @@ public:
       __ranges_.push_back(
           std::make_pair(__traits_.transform(__b.begin(), __b.end()), __traits_.transform(__e.begin(), __e.end())));
     } else {
-      if (__b.size() != 1 || __e.size() != 1)
+      if (__b.size() != 1 || __e.size() != 1 || __b[0] > __e[0])
         __throw_regex_error<regex_constants::error_range>();
       if (__icase_) {
         __b[0] = __traits_.translate_nocase(__b[0]);

libcxx/include/regex

@@ -2120,7 +2120,7 @@ public:
       __ranges_.push_back(
           std::make_pair(__traits_.transform(__b.begin(), __b.end()), __traits_.transform(__e.begin(), __e.end())));
     } else {
-      if (__b.size() != 1 || __e.size() != 1)
+      if (__b.size() != 1 || __e.size() != 1 || __b[0] > __e[0])
         std::__throw_regex_error<regex_constants::error_range>();
       if (__icase_) {
         __b[0] = __traits_.translate_nocase(__b[0]);

libcxx/test/std/re/re.regex/re.regex.construct/bad_range.pass.cpp

@@ -33,6 +33,7 @@ int main(int, char**)
 {
     assert(error_range_thrown("([\\w-a])"));
     assert(error_range_thrown("([a-\\w])"));
+    assert(error_range_thrown("([w-a])"));
 
-  return 0;
+    return 0;
 }