From: Jonathan Wakely <jwakely@redhat.com>
Date: Wed, 8 Dec 2021 19:36:24 +0000 (+0000)
Subject: libstdc++: Fix undefined shift when _Atomic_word is 64-bit
X-Git-Tag: basepoints/gcc-13~2465
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c15aa46cca0649b68613d3292cf71c7cc57ef78f;p=thirdparty%2Fgcc.git

libstdc++: Fix undefined shift when _Atomic_word is 64-bit

The check for _Atomic_word being 32-bit is just a normal runtime
condition for C++11 and C++14, because it doesn't use if-constexpr. That
means the 1LL << (CHAR_BIT * sizeof(_Atomic_word)) expression expands to
1LL << 64 on Solaris, which is ill-formed.

This adds another indirection so that the shift width is zero if the
code is unreachable.

libstdc++-v3/ChangeLog:

	* include/bits/shared_ptr_base.h (_Sp_counted_base::_M_release()):
	Make shift width conditional on __double_word condition.
---

diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h
index 90ad30947b04..f315d8f354fa 100644
--- a/libstdc++-v3/include/bits/shared_ptr_base.h
+++ b/libstdc++-v3/include/bits/shared_ptr_base.h
@@ -325,8 +325,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr bool __aligned = __alignof(long long) <= alignof(void*);
       if _GLIBCXX17_CONSTEXPR (__lock_free && __double_word && __aligned)
 	{
-	  constexpr long long __unique_ref
-	    = 1LL + (1LL << (__CHAR_BIT__ * sizeof(_Atomic_word)));
+	  constexpr int __wordbits = __CHAR_BIT__ * sizeof(_Atomic_word);
+	  constexpr int __shiftbits = __double_word ? __wordbits : 0;
+	  constexpr long long __unique_ref = 1LL + (1LL << __shiftbits);
 	  auto __both_counts = reinterpret_cast<long long*>(&_M_use_count);
 
 	  _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(&_M_weak_count);