From 640ebeb336050887cb57417b7568279c588088f0 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Fri, 20 Nov 2020 11:30:33 +0000
Subject: [PATCH] libstdc++: Remove <memory_resource> dependency from <regex>
 [PR 92546]

Unlike the other headers that declare alias templates in namespace pmr,
<regex> includes <memory_resource>. That was done because the
pmr::string::const_iterator typedef requires pmr::string to be complete,
which requires pmr::polymorphic_allocator<char> to be complete.

By using __normal_iterator<const char*, pmr::string> instead of the
const_iterator typedef we can avoid the completeness requirement.

This makes <regex> smaller, by not requiring <memory_resource> and its
<shared_mutex> dependency, which depends on <chrono>.  Backporting this
will also help with PR 97876, where <stop_token> ends up being needed by
<regex> via <memory_resource>.

libstdc++-v3/ChangeLog:

	PR libstdc++/92546
	* include/std/regex (pmr::smatch, pmr::wsmatch): Declare using
	underlying __normal_iterator type, not nested typedef
	basic_string::const_iterator.
---
 libstdc++-v3/include/std/regex | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/libstdc++-v3/include/std/regex b/libstdc++-v3/include/std/regex
index 43ee1aee616..783f5f131a6 100644
--- a/libstdc++-v3/include/std/regex
+++ b/libstdc++-v3/include/std/regex
@@ -64,21 +64,25 @@
 #include <bits/regex_executor.h>
 
 #if __cplusplus >= 201703L && _GLIBCXX_USE_CXX11_ABI
-#include <memory_resource>
 namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
-  namespace pmr {
+  namespace pmr
+  {
     template<typename _Tp> class polymorphic_allocator;
     template<typename _BidirectionalIterator>
       using match_results
 	= std::match_results<_BidirectionalIterator, polymorphic_allocator<
 				sub_match<_BidirectionalIterator>>>;
-    using cmatch  = match_results<const char*>;
-    using smatch  = match_results<string::const_iterator>;
+    using cmatch = match_results<const char*>;
+    // Use __normal_iterator directly, because pmr::string::const_iterator
+    // would require pmr::polymorphic_allocator to be complete.
+    using smatch
+      = match_results<__gnu_cxx::__normal_iterator<const char*, string>>;
 #ifdef _GLIBCXX_USE_WCHAR_T
     using wcmatch = match_results<const wchar_t*>;
-    using wsmatch = match_results<wstring::const_iterator>;
+    using wsmatch
+      = match_results<__gnu_cxx::__normal_iterator<const wchar_t*, wstring>>;
 #endif
   } // namespace pmr
 _GLIBCXX_END_NAMESPACE_VERSION
-- 
2.30.2