libstdc++: Do not use C++11 alignof in C++98 mode [PR104395]

When -faligned-new (or Clang's -faligned-allocation) is used our
allocators try to support extended alignments, gated on the
__cpp_aligned_new macro. However, because they use alignof(_Tp) which is
not a keyword in C++98 mode, using -std=c++98 -faligned-new results in
errors from <memory> and other headers.

We could change them to use __alignof__ instead of alignof, but that
would potentially alter the result of the conditions, because e.g.
alignof(long long) != __alignof__(long long) on some targets. That's
probably not an issue for any types with extended alignment, so maybe it
would be a safe change.

For now, it seems acceptable to just disable the extended alignment
support in C++98 mode, so that -faligned-new enables std::align_val_t
and the corresponding operator new overloads, but doesn't affect
std::allocator, __gnu_cxx::__bitmap_allocator etc.

libstdc++-v3/ChangeLog:

	PR libstdc++/104395
	* include/bits/new_allocator.h: Disable extended alignment
	support in C++98 mode.
	* include/bits/stl_tempbuf.h: Likewise.
	* include/ext/bitmap_allocator.h: Likewise.
	* include/ext/malloc_allocator.h: Likewise.
	* include/ext/mt_allocator.h: Likewise.
	* include/ext/pool_allocator.h: Likewise.
	* testsuite/ext/104395.cc: New test.

7 files changed, 20 insertions, 12 deletions

diff --git a/libstdc++-v3/include/bits/new_allocator.h b/libstdc++-v3/include/bits/new_allocator.h
index 0e90c88..5dcdee1 100644
--- a/libstdc++-v3/include/bits/new_allocator.h
+++ b/libstdc++-v3/include/bits/new_allocator.h
@@ -140,7 +140,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	    std::__throw_bad_alloc();
 	  }
 
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 	if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	  {
 	    std::align_val_t __al = std::align_val_t(alignof(_Tp));
@@ -161,7 +161,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 # define _GLIBCXX_SIZED_DEALLOC(p, n) (p)
 #endif
 
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 	if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	  {
 	    _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(__p, __n),
diff --git a/libstdc++-v3/include/bits/stl_tempbuf.h b/libstdc++-v3/include/bits/stl_tempbuf.h
index 759c493..0f26705 100644
--- a/libstdc++-v3/include/bits/stl_tempbuf.h
+++ b/libstdc++-v3/include/bits/stl_tempbuf.h
@@ -85,7 +85,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	if (__builtin_expect(size_t(__len) > (size_t(-1) / sizeof(_Tp)), 0))
 	  return 0;
 
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 	if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	  return (_Tp*) _GLIBCXX_OPERATOR_NEW(__len * sizeof(_Tp),
 					      align_val_t(alignof(_Tp)),
@@ -107,7 +107,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 # define _GLIBCXX_SIZED_DEALLOC(T, p, n) (p)
 #endif
 
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 	if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	  {
 	    _GLIBCXX_OPERATOR_DELETE(_GLIBCXX_SIZED_DEALLOC(_Tp, __p, __len),
@@ -168,7 +168,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     inline void
     return_temporary_buffer(_Tp* __p)
     {
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
       if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	_GLIBCXX_OPERATOR_DELETE(__p, align_val_t(alignof(_Tp)));
       else
diff --git a/libstdc++-v3/include/ext/bitmap_allocator.h b/libstdc++-v3/include/ext/bitmap_allocator.h
index ef2ee13..45b2283 100644
--- a/libstdc++-v3/include/ext/bitmap_allocator.h
+++ b/libstdc++-v3/include/ext/bitmap_allocator.h
@@ -1017,7 +1017,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	if (__n > this->max_size())
 	  std::__throw_bad_alloc();
 
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 	if (alignof(value_type) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	  {
 	    const size_type __b = __n * sizeof(value_type);
@@ -1044,7 +1044,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       {
 	if (__builtin_expect(__p != 0, true))
 	  {
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 	    // Types with extended alignment are handled by operator delete.
 	    if (alignof(value_type) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	      {
diff --git a/libstdc++-v3/include/ext/malloc_allocator.h b/libstdc++-v3/include/ext/malloc_allocator.h
index b0a87b6..3651378 100644
--- a/libstdc++-v3/include/ext/malloc_allocator.h
+++ b/libstdc++-v3/include/ext/malloc_allocator.h
@@ -120,7 +120,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  }
 
 	_Tp* __ret = 0;
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 #if __cplusplus > 201402L && _GLIBCXX_HAVE_ALIGNED_ALLOC
 	if (alignof(_Tp) > alignof(std::max_align_t))
 	  {
diff --git a/libstdc++-v3/include/ext/mt_allocator.h b/libstdc++-v3/include/ext/mt_allocator.h
index 0b0bf8d..77f7dcd 100644
--- a/libstdc++-v3/include/ext/mt_allocator.h
+++ b/libstdc++-v3/include/ext/mt_allocator.h
@@ -693,7 +693,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       if (__n > this->max_size())
 	std::__throw_bad_alloc();
 
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
       // Types with extended alignment are handled by operator new/delete.
       if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	{
@@ -748,7 +748,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       if (__builtin_expect(__p != 0, true))
 	{
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 	  // Types with extended alignment are handled by operator new/delete.
 	  if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	    {
diff --git a/libstdc++-v3/include/ext/pool_allocator.h b/libstdc++-v3/include/ext/pool_allocator.h
index 13895b2..679b4b3 100644
--- a/libstdc++-v3/include/ext/pool_allocator.h
+++ b/libstdc++-v3/include/ext/pool_allocator.h
@@ -224,7 +224,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 	  const size_t __bytes = __n * sizeof(_Tp);
 
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 	  if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	    {
 	      std::align_val_t __al = std::align_val_t(alignof(_Tp));
@@ -272,7 +272,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       using std::size_t;
       if (__builtin_expect(__n != 0 && __p != 0, true))
 	{
-#if __cpp_aligned_new
+#if __cpp_aligned_new && __cplusplus >= 201103L
 	  if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
 	    {
 	      ::operator delete(__p, std::align_val_t(alignof(_Tp)));
diff --git a/libstdc++-v3/testsuite/ext/104395.cc b/libstdc++-v3/testsuite/ext/104395.cc
new file mode 100644
index 0000000..252c40c
--- /dev/null
+++ b/libstdc++-v3/testsuite/ext/104395.cc
@@ -0,0 +1,8 @@
+// { dg-options "-std=gnu++98 -faligned-new" }
+// { dg-do compile }
+#include <ext/memory>
+#include <ext/bitmap_allocator.h>
+#include <ext/mt_allocator.h>
+#include <ext/malloc_allocator.h>
+#include <ext/new_allocator.h>
+#include <ext/pool_allocator.h>