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re PR c++/65945 (C++ alignment of nullptr_t is 1 and might cause unaligned stores to the frame)

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PR c++/65945
	* decl.c (cxx_init_decl_processing): Set TYPE_ALIGN of nullptr_t.
	* class.c (layout_nonempty_base_or_field): Warn if that affects
	the offset of a field.

From-SVN: r225270
This commit is contained in:
Jason Merrill 2015-07-01 13:59:19 -04:00 • committed by Jason Merrill
parent f9a12f7b8f
commit d68f848b12
5 changed files with 53 additions and 0 deletions
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7
gcc/cp/ChangeLog
View file

@ -1,3 +1,10 @@
2015-07-01 Jason Merrill <jason@redhat.com>
PR c++/65945
* decl.c (cxx_init_decl_processing): Set TYPE_ALIGN of nullptr_t.
* class.c (layout_nonempty_base_or_field): Warn if that affects
the offset of a field.
2015-07-01 Paolo Carlini <paolo.carlini@oracle.com>
PR c++/60365

19
gcc/cp/class.c
View file

@ -4281,6 +4281,25 @@ layout_nonempty_base_or_field (record_layout_info rli,
: TYPE_ALIGN (type)));
normalize_rli (rli);
}
else if (TREE_CODE (type) == NULLPTR_TYPE
&& warn_abi && abi_version_crosses (9))
{
/* Before ABI v9, we were giving nullptr_t alignment of 1; if
the offset wasn't aligned like a pointer when we started to
layout this field, that affects its position. */
tree pos = rli_size_unit_so_far (&old_rli);
if (int_cst_value (pos) % TYPE_ALIGN_UNIT (ptr_type_node) != 0)
{
if (abi_version_at_least (9))
warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wabi,
"alignment of %qD increased in -fabi-version=9 "
"(GCC 5.2)", decl);
else
warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wabi, "alignment "
"of %qD will increase in -fabi-version=9", decl);
}
break;
}
else
/* There was no conflict. We're done laying out this field. */
break;

2
gcc/cp/decl.c
View file

@ -4007,6 +4007,8 @@ cxx_init_decl_processing (void)
TYPE_SIZE_UNIT (nullptr_type_node) = size_int (GET_MODE_SIZE (ptr_mode));
TYPE_UNSIGNED (nullptr_type_node) = 1;
TYPE_PRECISION (nullptr_type_node) = GET_MODE_BITSIZE (ptr_mode);
if (abi_version_at_least (9))
TYPE_ALIGN (nullptr_type_node) = GET_MODE_ALIGNMENT (ptr_mode);
SET_TYPE_MODE (nullptr_type_node, ptr_mode);
record_builtin_type (RID_MAX, "decltype(nullptr)", nullptr_type_node);
nullptr_node = build_int_cst (nullptr_type_node, 0);

5
gcc/testsuite/g++.dg/abi/nullptr-align.C Normal file
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@ -0,0 +1,5 @@
// PR c++/65945
// { dg-do compile { target c++11 } }
// { dg-options "-fabi-version=9" }
static_assert(alignof (decltype (nullptr)) == alignof (void *), "");

20
gcc/testsuite/g++.dg/abi/nullptr-align2.C Normal file
View file

@ -0,0 +1,20 @@
// { dg-do compile { target c++11 } }
// { dg-options "-fabi-version=0 -Wabi=8" }
struct A
{
decltype(nullptr) n;
decltype(nullptr) n2;
};
struct B
{
void *p;
decltype(nullptr) n;
};
struct C
{
char c;
decltype(nullptr) n; // { dg-warning "alignment" }
};