Question

有人可以帮助我找到位置或解释__attribute_malloc__的含义吗？还有__wur吗？

我正在使用大约120个fortran f77文件的旧代码，但是使用了一些C文件，其中仅使用malloc()，而它们使用# include <malloc.h>。

我有kdiff'd stdlib.h和malloc.h；不确定我可以在这两种实现之间找到任何区别吗？

使用的Linux发行版可以负责/usr/include/malloc.h的内容吗？我正在使用具有GCC 4.3.4的SLES 11.4 x86-64，这里是/usr/include/malloc.h：

/* Prototypes and definition for malloc implementation.
   Copyright (C) 1996, 1997, 1999, 2000, 2002-2004, 2005, 2007, 2009
   Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#ifndef _MALLOC_H
#define _MALLOC_H 1

#include <features.h>
#include <stddef.h>
#include <stdio.h>

# define __malloc_ptr_t  void *

/* Used by GNU libc internals. */
#define __malloc_size_t size_t
#define __malloc_ptrdiff_t ptrdiff_t

#ifdef __GNUC__

# define __MALLOC_P(args)   args __THROW
/* This macro will be used for functions which might take C++ callback functions.  */
# define __MALLOC_PMT(args) args

#else   /* Not GCC.  */

# define __MALLOC_P(args)   args
# define __MALLOC_PMT(args) args

#endif  /* GCC.  */


__BEGIN_DECLS

/* Allocate SIZE bytes of memory.  */
extern void *malloc __MALLOC_P ((size_t __size)) __attribute_malloc__ __wur;

/* Allocate NMEMB elements of SIZE bytes each, all initialized to 0.  */
extern void *calloc __MALLOC_P ((size_t __nmemb, size_t __size)) __attribute_malloc__ __wur;

/* Re-allocate the previously allocated block in __ptr, making the new block SIZE bytes long.  */
/* __attribute_malloc__ is not used, because if realloc returns
   the same pointer that was passed to it, aliasing needs to be allowed
   between objects pointed by the old and new pointers.  */
extern void *realloc __MALLOC_P ((void *__ptr, size_t __size)) __attribute_warn_unused_result__;

/* Free a block allocated by `malloc', `realloc' or `calloc'.  */
extern void free __MALLOC_P ((void *__ptr));

/* Free a block allocated by `calloc'. */
extern void cfree __MALLOC_P ((void *__ptr));

/* Allocate SIZE bytes allocated to ALIGNMENT bytes.  */
extern void *memalign __MALLOC_P ((size_t __alignment, size_t __size)) __attribute_malloc__ __wur;

/* Allocate SIZE bytes on a page boundary.  */
extern void *valloc __MALLOC_P ((size_t __size)) __attribute_malloc__ __wur;

/* Equivalent to valloc(minimum-page-that-holds(n)), that is, round up __size to nearest pagesize. */
extern void * pvalloc __MALLOC_P ((size_t __size)) __attribute_malloc__ __wur;

/* Underlying allocation function; successive calls should return contiguous pieces of memory.  */
extern void *(*__morecore) __MALLOC_PMT ((ptrdiff_t __size));

/* Default value of `__morecore'.  */
extern void *__default_morecore __MALLOC_P ((ptrdiff_t __size)) __attribute_malloc__;

/* SVID2/XPG mallinfo structure */

struct mallinfo {
  int arena;    /* non-mmapped space allocated from system */
  int ordblks;  /* number of free chunks */
  int smblks;   /* number of fastbin blocks */
  int hblks;    /* number of mmapped regions */
  int hblkhd;   /* space in mmapped regions */
  int usmblks;  /* maximum total allocated space */
  int fsmblks;  /* space available in freed fastbin blocks */
  int uordblks; /* total allocated space */
  int fordblks; /* total free space */
  int keepcost; /* top-most, releasable (via malloc_trim) space */
};

/* Returns a copy of the updated current mallinfo. */
extern struct mallinfo mallinfo __MALLOC_P ((void));

/* SVID2/XPG mallopt options */
#ifndef M_MXFAST
# define M_MXFAST  1    /* maximum request size for "fastbins" */
#endif
#ifndef M_NLBLKS
# define M_NLBLKS  2    /* UNUSED in this malloc */
#endif
#ifndef M_GRAIN
# define M_GRAIN   3    /* UNUSED in this malloc */
#endif
#ifndef M_KEEP
# define M_KEEP    4    /* UNUSED in this malloc */
#endif

/* mallopt options that actually do something */
#define M_TRIM_THRESHOLD    -1
#define M_TOP_PAD           -2
#define M_MMAP_THRESHOLD    -3
#define M_MMAP_MAX          -4
#define M_CHECK_ACTION      -5
#define M_PERTURB       -6
#define M_ARENA_TEST        -7
#define M_ARENA_MAX     -8

/* General SVID/XPG interface to tunable parameters. */
extern int mallopt __MALLOC_P ((int __param, int __val));

/* Release all but __pad bytes of freed top-most memory back to the
   system. Return 1 if successful, else 0. */
extern int malloc_trim __MALLOC_P ((size_t __pad));

/* Report the number of usable allocated bytes associated with allocated chunk __ptr. */
extern size_t malloc_usable_size __MALLOC_P ((void *__ptr));

/* Prints brief summary statistics on stderr. */
extern void malloc_stats __MALLOC_P ((void));

/* Output information about state of allocator to stream FP.  */
extern int malloc_info (int __options, FILE *__fp);

/* Record the state of all malloc variables in an opaque data structure. */
extern void *malloc_get_state __MALLOC_P ((void));

/* Restore the state of all malloc variables from data obtained with malloc_get_state(). */
extern int malloc_set_state __MALLOC_P ((void *__ptr));

/* Called once when malloc is initialized; redefining this variable in
   the application provides the preferred way to set up the hook pointers. */
extern void (*__malloc_initialize_hook) __MALLOC_PMT ((void));

/* Hooks for debugging and user-defined versions. */
extern void (*__free_hook) __MALLOC_PMT ((void *__ptr, __const __malloc_ptr_t));
extern void *(*__malloc_hook) __MALLOC_PMT ((size_t __size, __const __malloc_ptr_t));
extern void *(*__realloc_hook) __MALLOC_PMT ((void *__ptr, size_t __size, __const __malloc_ptr_t));
extern void *(*__memalign_hook) __MALLOC_PMT ((size_t __alignment, size_t __size, __const __malloc_ptr_t));
extern void (*__after_morecore_hook) __MALLOC_PMT ((void));

/* Activate a standard set of debugging hooks. */
extern void __malloc_check_init __MALLOC_P ((void));


__END_DECLS

#endif /* malloc.h */

Answer 1

如果您的代码仅使用标准的内存分配接口（malloc，realloc，calloc和free），则应包括stdlib.h，并且您应该不包括malloc.h。 malloc.h是一个非标准的标头，其存在有两个原因：与某些1980年代时代的向后兼容性，预标准化的C库以及在声明malloc接口的扩展的地方，因此它们不会污染不使用它们的人的名称空间。 stdlib.h是从中获取内存分配功能的标准位置。它还声明了其他与内存分配无关的其他内容。取malloc.h和stdlib.h之间的区别不会告诉您任何有用的信息。

您无需关心__attribute_malloc__或__wur（或__THROW，或者通常不在C库头文件中的任何东西，以及其名称，以两个下划线开头）。它们是C库使用的注释，用于与C编译器就“不是您的问题”进行沟通。 {em>假定在malloc中的malloc.h声明与malloc中的stdlib.h声明完全相同，包括所有注释；如果不是，那么这是C库中的错误。由于这是您要查看其标题的GNU C库，因此我通常会告诉您在https://sourceware.org/bugzilla/提交错误报告，但是您引用的malloc.h比当前的开发系列还早十年。，而我刚刚检查了它们与当前开发系列中的相同，因此，如果存在差异，那是因为您的Linux发行版已过时，因此您应该与他们合作，而不是与GNU libc上游。

但是，为了满足您的好奇心，我将告诉您注释的含义。 __attribute_malloc__和__wur是sys/cdefs.h中定义的宏（GNU libc中的每个公共头文件都间接包含了这些宏）。根据{{1}}的值，__attribute_malloc__扩展为__attribute__ ((__malloc__))，__wur扩展为__attribute__ ((__warn_unused_result__))或什么都不扩展。

这两个_FORTIFY_SOURCE构造都记录在the GCC manual中。 __attribute__ ((...))属性告诉编译器，这是一个“类似于malloc的函数，即，该函数返回的指针P不能在该函数返回时别名任何其他有效的指针，而且没有指向有效对象的指针出现在由P''寻址的任何存储中，这有助于优化器一点点地完成。（即使没有声明使用声明，GCC的当前版本也已经知道malloc，但较旧的版本则没有。）malloc属性“导致如果调用者发出警告，具有该属性的函数不使用它的返回值”，这对于warn_unused_result来说是一项安全功能，因为如果调用malloc并且不使用它的返回值，则会导致内存泄漏。 / p>

了解malloc.h的区别：__attribute_malloc__

1 个答案: