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From: Jonathan Wakely <redi@gcc.gnu.org>
To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org
Subject: [gcc r11-5199] libstdc++: Remove <memory_resource> dependency from
 <regex> [PR 92546]
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https://gcc.gnu.org/g:640ebeb336050887cb57417b7568279c588088f0

commit r11-5199-g640ebeb336050887cb57417b7568279c588088f0
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Nov 20 11:30:33 2020 +0000

    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.

Diff:
---
 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