284a0e3cbf
Since we use obstacks with objects that are not default constructible, we sometimes need to manually call the constructor by hand using placement new: foo *f = obstack_alloc (obstack, sizeof (foo)); f = new (f) foo; It's possible to use allocate_on_obstack instead, but there are types that we sometimes want to allocate on an obstack, and sometimes on the regular heap. This patch introduces a utility to make this pattern simpler if allocate_on_obstack is not an option: foo *f = obstack_new<foo> (obstack); Right now there's only one usage (in tdesc_data_init). To help catch places where we would forget to call new when allocating such an object on an obstack, this patch also poisons some other methods of allocating an instance of a type on an obstack: - OBSTACK_ZALLOC/OBSTACK_CALLOC - XOBNEW/XOBNEW - GDBARCH_OBSTACK_ZALLOC/GDBARCH_OBSTACK_CALLOC Unfortunately, there's no way to catch wrong usages of obstack_alloc. By pulling on that string though, it tripped on allocating struct template_symbol using OBSTACK_ZALLOC. The criterion currently used to know whether it's safe to "malloc" an instance of a struct is whether it is a POD. Because it inherits from struct symbol, template_symbol is not a POD. This criterion is a bit too strict however, it should still safe to allocate memory for a template_symbol and memset it to 0. We didn't use is_trivially_constructible as the criterion in the first place only because it is not available in gcc < 5. So here I considered two alternatives: 1. Relax that criterion to use std::is_trivially_constructible and add a bit more glue code to make it work with gcc < 5 2. Continue pulling on the string and change how the symbol structures are allocated and initialized I managed to do both, but I decided to go with #1 to keep this patch simpler and more focused. When building with a compiler that does not have is_trivially_constructible, the check will just not be enforced. gdb/ChangeLog: * common/traits.h (HAVE_IS_TRIVIALLY_COPYABLE): Define if compiler supports std::is_trivially_constructible. * common/poison.h: Include obstack.h. (IsMallocable): Define to is_trivially_constructible if the compiler supports it, define to true_type otherwise. (xobnew): New. (XOBNEW): Redefine. (xobnewvec): New. (XOBNEWVEC): Redefine. * gdb_obstack.h (obstack_zalloc): New. (OBSTACK_ZALLOC): Redefine. (obstack_calloc): New. (OBSTACK_CALLOC): Redefine. (obstack_new): New. * gdbarch.sh: Include gdb_obstack in gdbarch.h. (gdbarch_obstack): New declaration in gdbarch.h, definition in gdbarch.c. (GDBARCH_OBSTACK_CALLOC, GDBARCH_OBSTACK_ZALLOC): Use obstack_calloc/obstack_zalloc. (gdbarch_obstack_zalloc): Remove. * target-descriptions.c (tdesc_data_init): Use obstack_new.
130 lines
4.0 KiB
C++
130 lines
4.0 KiB
C++
/* Obstack wrapper for GDB.
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Copyright (C) 2002-2018 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#if !defined (GDB_OBSTACK_H)
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#define GDB_OBSTACK_H 1
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#include "obstack.h"
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/* Utility macros - wrap obstack alloc into something more robust. */
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template <typename T>
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static inline T*
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obstack_zalloc (struct obstack *ob)
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{
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static_assert (IsMallocable<T>::value, "Trying to use OBSTACK_ZALLOC with a \
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non-POD data type. Use obstack_new instead.");
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return ((T *) memset (obstack_alloc (ob, sizeof (T)), 0, sizeof (T)));
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}
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#define OBSTACK_ZALLOC(OBSTACK,TYPE) obstack_zalloc<TYPE> ((OBSTACK))
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template <typename T>
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static inline T *
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obstack_calloc (struct obstack *ob, size_t number)
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{
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static_assert (IsMallocable<T>::value, "Trying to use OBSTACK_CALLOC with a \
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non-POD data type. Use obstack_new instead.");
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return ((T *) memset (obstack_alloc (ob, number * sizeof (T)), 0,
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number * sizeof (T)));
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}
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#define OBSTACK_CALLOC(OBSTACK,NUMBER,TYPE) \
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obstack_calloc<TYPE> ((OBSTACK), (NUMBER))
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/* Allocate an object on OB and call its constructor. */
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template <typename T, typename... Args>
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static inline T*
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obstack_new (struct obstack *ob, Args&&... args)
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{
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T* object = (T *) obstack_alloc (ob, sizeof (T));
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object = new (object) T (std::forward<Args> (args)...);
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return object;
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}
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/* Unless explicitly specified, GDB obstacks always use xmalloc() and
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xfree(). */
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/* Note: ezannoni 2004-02-09: One could also specify the allocation
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functions using a special init function for each obstack,
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obstack_specify_allocation. However we just use obstack_init and
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let these defines here do the job. While one could argue the
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superiority of one approach over the other, we just chose one
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throughout. */
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#define obstack_chunk_alloc xmalloc
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#define obstack_chunk_free xfree
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#define obstack_grow_str(OBSTACK,STRING) \
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obstack_grow (OBSTACK, STRING, strlen (STRING))
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#define obstack_grow_str0(OBSTACK,STRING) \
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obstack_grow0 (OBSTACK, STRING, strlen (STRING))
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#define obstack_grow_wstr(OBSTACK, WSTRING) \
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obstack_grow (OBSTACK, WSTRING, sizeof (gdb_wchar_t) * gdb_wcslen (WSTRING))
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/* Concatenate NULL terminated variable argument list of `const char
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*' strings; return the new string. Space is found in the OBSTACKP.
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Argument list must be terminated by a sentinel expression `(char *)
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NULL'. */
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extern char *obconcat (struct obstack *obstackp, ...) ATTRIBUTE_SENTINEL;
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/* Duplicate STRING, returning an equivalent string that's allocated on the
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obstack OBSTACKP. */
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extern char *obstack_strdup (struct obstack *obstackp, const char *string);
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/* An obstack that frees itself on scope exit. */
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struct auto_obstack : obstack
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{
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auto_obstack ()
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{ obstack_init (this); }
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~auto_obstack ()
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{ obstack_free (this, NULL); }
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/* Free all memory in the obstack but leave it valid for further
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allocation. */
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void clear ()
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{ obstack_free (this, obstack_base (this)); }
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};
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/* Objects are allocated on obstack instead of heap. */
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struct allocate_on_obstack
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{
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allocate_on_obstack () = default;
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void* operator new (size_t size, struct obstack *obstack)
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{
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return obstack_alloc (obstack, size);
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}
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void* operator new[] (size_t size, struct obstack *obstack)
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{
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return obstack_alloc (obstack, size);
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}
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void operator delete (void *memory) {}
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void operator delete[] (void *memory) {}
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};
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#endif
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