[gcc/devel/ranger] libstdc++: Fix incorrect size calculation in PMR resource (PR 94906)

[Aldy Hernandez <aldyh@gcc.gnu.org>]

https://gcc.gnu.org/g:bb27781b64162e1769df15e0c97e8d2145d2d10d

commit bb27781b64162e1769df15e0c97e8d2145d2d10d
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon May 4 21:13:28 2020 +0100

    libstdc++: Fix incorrect size calculation in PMR resource  (PR 94906)
    
    Calculating the size of a chunk being returned to the upstream allocator
    was done with a 32-bit type, so it wrapped if the chunk was 4GB or
    larger.
    
    I don't know how to test this without allocating 4GB, so there's no test
    in the testsuite. It has been tested manually with allocations sizes and
    alignments exceeding 4GB.
    
            PR libstdc++/94906
            * src/c++17/memory_resource.cc
            (monotonic_buffer_resource::_Chunk::release): Use size_t for shift
            operands.

Diff:
---
 libstdc++-v3/ChangeLog                    | 7 +++++++
 libstdc++-v3/src/c++17/memory_resource.cc | 4 ++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 739ab9eeb29..9cc811c884f 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,10 @@
+2020-05-04  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/94906
+	* src/c++17/memory_resource.cc
+	(monotonic_buffer_resource::_Chunk::release): Use size_t for shift
+	operands.
+
 2020-05-04  Nathan Sidwell  <nathan@acm.org>
 
 	PR libstdc++/94747
diff --git a/libstdc++-v3/src/c++17/memory_resource.cc b/libstdc++-v3/src/c++17/memory_resource.cc
index 1acab19e306..95352b23537 100644
--- a/libstdc++-v3/src/c++17/memory_resource.cc
+++ b/libstdc++-v3/src/c++17/memory_resource.cc
@@ -228,8 +228,8 @@ namespace pmr
 	  if (__ch->_M_canary != (__ch->_M_size | __ch->_M_align))
 	    return; // buffer overflow detected!
 
-	  size_t __size = (1u << __ch->_M_size);
-	  size_t __align = (1u << __ch->_M_align);
+	  size_t __size = (size_t)1 << __ch->_M_size;
+	  size_t __align = (size_t)1 << __ch->_M_align;
 	  void* __start = (char*)(__ch + 1) - __size;
 	  __r->deallocate(__start, __size, __align);
 	}