Introduce obstack_new, poison other "typed" obstack functions
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.
This commit is contained in:
Simon Marchi
Simon Marchi
parent
b1aed5de0c
commit
284a0e3cbf
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@ -1,3 +1,27 @@
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2018-05-20 Simon Marchi <simon.marchi@ericsson.com>
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* common/traits.h (HAVE_IS_TRIVIALLY_COPYABLE): Define if
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compiler supports std::is_trivially_constructible.
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* common/poison.h: Include obstack.h.
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(IsMallocable): Define to is_trivially_constructible if the
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compiler supports it, define to true_type otherwise.
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(xobnew): New.
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(XOBNEW): Redefine.
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(xobnewvec): New.
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(XOBNEWVEC): Redefine.
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* gdb_obstack.h (obstack_zalloc): New.
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(OBSTACK_ZALLOC): Redefine.
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(obstack_calloc): New.
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(OBSTACK_CALLOC): Redefine.
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(obstack_new): New.
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* gdbarch.sh: Include gdb_obstack in gdbarch.h.
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(gdbarch_obstack): New declaration in gdbarch.h, definition in
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gdbarch.c.
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(GDBARCH_OBSTACK_CALLOC, GDBARCH_OBSTACK_ZALLOC): Use
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obstack_calloc/obstack_zalloc.
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(gdbarch_obstack_zalloc): Remove.
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* target-descriptions.c (tdesc_data_init): Use obstack_new.
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2018-05-19 Philippe Waroquiers <philippe.waroquiers@skynet.be>
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* stack.c (backtrace_command_1): Remove useless variable int i.
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@ -21,6 +21,7 @@
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#define COMMON_POISON_H
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#include "traits.h"
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#include "obstack.h"
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/* Poison memset of non-POD types. The idea is catching invalid
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initialization of non-POD structs that is easy to be introduced as
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@ -88,7 +89,11 @@ void *memmove (D *dest, const S *src, size_t n) = delete;
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objects that require new/delete. */
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template<typename T>
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using IsMallocable = std::is_pod<T>;
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#if HAVE_IS_TRIVIALLY_CONSTRUCTIBLE
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using IsMallocable = std::is_trivially_constructible<T>;
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#else
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using IsMallocable = std::true_type;
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#endif
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template<typename T>
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using IsFreeable = gdb::Or<std::is_trivially_destructible<T>, std::is_void<T>>;
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@ -216,4 +221,28 @@ non-POD data type.");
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#undef XRESIZEVAR
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#define XRESIZEVAR(T, P, S) xresizevar<T> (P, S)
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template<typename T>
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static T *
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xobnew (obstack *ob)
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{
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static_assert (IsMallocable<T>::value, "Trying to use XOBNEW with a \
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non-POD data type.");
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return XOBNEW (ob, T);
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}
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#undef XOBNEW
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#define XOBNEW(O, T) xobnew<T> (O)
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template<typename T>
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static T *
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xobnewvec (obstack *ob, size_t n)
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{
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static_assert (IsMallocable<T>::value, "Trying to use XOBNEWVEC with a \
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non-POD data type.");
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return XOBNEWVEC (ob, T, n);
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}
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#undef XOBNEWVEC
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#define XOBNEWVEC(O, T, N) xobnewvec<T> (O, N)
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#endif /* COMMON_POISON_H */
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@ -33,6 +33,14 @@
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# define HAVE_IS_TRIVIALLY_COPYABLE 1
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#endif
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/* HAVE_IS_TRIVIALLY_CONSTRUCTIBLE is defined as 1 iff
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std::is_trivially_constructible is available. GCC only implemented it
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in GCC 5. */
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#if (__has_feature(is_trivially_constructible) \
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|| (defined __GNUC__ && __GNUC__ >= 5))
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# define HAVE_IS_TRIVIALLY_COPYABLE 1
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#endif
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namespace gdb {
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/* Pre C++14-safe (CWG 1558) version of C++17's std::void_t. See
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@ -24,12 +24,40 @@
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/* Utility macros - wrap obstack alloc into something more robust. */
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#define OBSTACK_ZALLOC(OBSTACK,TYPE) \
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((TYPE *) memset (obstack_alloc ((OBSTACK), sizeof (TYPE)), 0, sizeof (TYPE)))
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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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((TYPE *) memset (obstack_alloc ((OBSTACK), (NUMBER) * sizeof (TYPE)), \
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0, (NUMBER) * sizeof (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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@ -471,15 +471,10 @@ gdbarch_alloc (const struct gdbarch_info *info,
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}
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/* Allocate extra space using the per-architecture obstack. */
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void *
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gdbarch_obstack_zalloc (struct gdbarch *arch, long size)
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obstack *gdbarch_obstack (gdbarch *arch)
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{
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void *data = obstack_alloc (arch->obstack, size);
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memset (data, 0, size);
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return data;
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return arch->obstack;
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}
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/* See gdbarch.h. */
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@ -38,6 +38,7 @@
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#include <vector>
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#include "frame.h"
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#include "dis-asm.h"
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#include "gdb_obstack.h"
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struct floatformat;
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struct ui_file;
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@ -1705,14 +1706,17 @@ extern struct gdbarch *gdbarch_alloc (const struct gdbarch_info *info, struct gd
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extern void gdbarch_free (struct gdbarch *);
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/* Get the obstack owned by ARCH. */
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extern obstack *gdbarch_obstack (gdbarch *arch);
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/* Helper function. Allocate memory from the ``struct gdbarch''
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obstack. The memory is freed when the corresponding architecture
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is also freed. */
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extern void *gdbarch_obstack_zalloc (struct gdbarch *gdbarch, long size);
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#define GDBARCH_OBSTACK_CALLOC(GDBARCH, NR, TYPE) ((TYPE *) gdbarch_obstack_zalloc ((GDBARCH), (NR) * sizeof (TYPE)))
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#define GDBARCH_OBSTACK_ZALLOC(GDBARCH, TYPE) ((TYPE *) gdbarch_obstack_zalloc ((GDBARCH), sizeof (TYPE)))
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#define GDBARCH_OBSTACK_CALLOC(GDBARCH, NR, TYPE) obstack_calloc<TYPE> (gdbarch_obstack ((GDBARCH)), (NR))
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#define GDBARCH_OBSTACK_ZALLOC(GDBARCH, TYPE) obstack_zalloc<TYPE> (gdbarch_obstack ((GDBARCH)))
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/* Duplicate STRING, returning an equivalent string that's allocated on the
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obstack associated with GDBARCH. The string is freed when the corresponding
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@ -1261,6 +1261,7 @@ cat <<EOF
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#include <vector>
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#include "frame.h"
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#include "dis-asm.h"
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#include "gdb_obstack.h"
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struct floatformat;
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struct ui_file;
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@ -1532,14 +1533,19 @@ extern struct gdbarch *gdbarch_alloc (const struct gdbarch_info *info, struct gd
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extern void gdbarch_free (struct gdbarch *);
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/* Get the obstack owned by ARCH. */
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extern obstack *gdbarch_obstack (gdbarch *arch);
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/* Helper function. Allocate memory from the \`\`struct gdbarch''
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obstack. The memory is freed when the corresponding architecture
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is also freed. */
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extern void *gdbarch_obstack_zalloc (struct gdbarch *gdbarch, long size);
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#define GDBARCH_OBSTACK_CALLOC(GDBARCH, NR, TYPE) ((TYPE *) gdbarch_obstack_zalloc ((GDBARCH), (NR) * sizeof (TYPE)))
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#define GDBARCH_OBSTACK_ZALLOC(GDBARCH, TYPE) ((TYPE *) gdbarch_obstack_zalloc ((GDBARCH), sizeof (TYPE)))
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#define GDBARCH_OBSTACK_CALLOC(GDBARCH, NR, TYPE) \
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obstack_calloc<TYPE> (gdbarch_obstack ((GDBARCH)), (NR))
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#define GDBARCH_OBSTACK_ZALLOC(GDBARCH, TYPE) \
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obstack_zalloc<TYPE> (gdbarch_obstack ((GDBARCH)))
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/* Duplicate STRING, returning an equivalent string that's allocated on the
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obstack associated with GDBARCH. The string is freed when the corresponding
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@ -1849,15 +1855,10 @@ EOF
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printf "\n"
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printf "\n"
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cat <<EOF
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/* Allocate extra space using the per-architecture obstack. */
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void *
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gdbarch_obstack_zalloc (struct gdbarch *arch, long size)
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obstack *gdbarch_obstack (gdbarch *arch)
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{
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void *data = obstack_alloc (arch->obstack, size);
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memset (data, 0, size);
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return data;
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return arch->obstack;
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}
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/* See gdbarch.h. */
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@ -723,12 +723,7 @@ tdesc_find_type (struct gdbarch *gdbarch, const char *id)
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static void *
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tdesc_data_init (struct obstack *obstack)
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{
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struct tdesc_arch_data *data;
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data = OBSTACK_ZALLOC (obstack, struct tdesc_arch_data);
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new (data) tdesc_arch_data ();
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return data;
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return obstack_new<tdesc_arch_data> (obstack);
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}
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/* Similar, but for the temporary copy used during architecture
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