09775d3718
If we consider simple objects as arrays of size 1, we can considerably
simplify these APIs, merging the *ARRAY and the non-array variants.
That will produce more readable code, since lines will be shorter (by
not having ARRAY in the macro names, as all macros will consistently
handle arrays), and the allocated size will be also more explicit.
The syntax will now be of the form:
p = MALLOC(42, foo_t); // allocate 42 elements of type foo_t.
p = MALLOC(1, bar_t); // allocate 1 element of type foo_t.
The _array() allocation functions should _never_ be called directly, and
instead these macros should be used.
The non-array functions (e.g., malloc(3)) still have their place, but
are limited to allocating structures with flexible array members. For
any other uses, the macros should be used.
Thus, we don't use any array or ARRAY variants in any code any more, and
they are only used as implementation details of these macros.
Link: <https://software.codidact.com/posts/285898/288023#answer-288023>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
119 lines
2.9 KiB
C
119 lines
2.9 KiB
C
/*
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* SPDX-FileCopyrightText: 2007 - 2009, Nicolas François
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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/*
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* According to the Linux-PAM documentation:
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*
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* 4.1. Care about standard library calls
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*
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* In general, writers of authorization-granting applications should
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* assume that each module is likely to call any or all 'libc' functions.
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* For 'libc' functions that return pointers to static/dynamically
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* allocated structures (ie. the library allocates the memory and the
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* user is not expected to 'free()' it) any module call to this function
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* is likely to corrupt a pointer previously obtained by the application.
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* The application programmer should either re-call such a 'libc'
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* function after a call to the Linux-PAM library, or copy the structure
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* contents to some safe area of memory before passing control to the
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* Linux-PAM library.
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*
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* Two important function classes that fall into this category are
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* getpwnam(3) and syslog(3).
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*
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* This file provides wrapper to the name or name_r functions.
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*/
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#include <unistd.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <errno.h>
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#include "alloc.h"
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#include "prototypes.h"
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#include "shadowlog.h"
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#define XFUNCTION_NAME XPREFIX (FUNCTION_NAME)
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#define XPREFIX(name) XPREFIX1 (name)
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#define XPREFIX1(name) x##name
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#define REENTRANT_NAME APPEND_R (FUNCTION_NAME)
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#define APPEND_R(name) APPEND_R1 (name)
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#define APPEND_R1(name) name##_r
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#define STRINGIZE(name) STRINGIZE1 (name)
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#define STRINGIZE1(name) #name
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/*@null@*/ /*@only@*/LOOKUP_TYPE *XFUNCTION_NAME (ARG_TYPE ARG_NAME)
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{
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#if HAVE_FUNCTION_R
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LOOKUP_TYPE *result=NULL;
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char *buffer=NULL;
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/* we have to start with something */
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size_t length = 0x100;
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result = MALLOC(1, LOOKUP_TYPE);
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if (NULL == result) {
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goto oom;
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}
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while (true) {
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int status;
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LOOKUP_TYPE *resbuf = NULL;
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buffer = XREALLOC(buffer, length, char);
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status = REENTRANT_NAME(ARG_NAME, result, buffer,
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length, &resbuf);
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if ((0 == status) && (resbuf == result)) {
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/* Build a result structure that can be freed by
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* the shadow *_free functions. */
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LOOKUP_TYPE *ret_result = DUP_FUNCTION(result);
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if (NULL == ret_result) {
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goto oom;
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}
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free(buffer);
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free(result);
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return ret_result;
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}
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if (ERANGE != status) {
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break;
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}
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if (length == SIZE_MAX) {
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break;
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}
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length = (length <= SIZE_MAX / 4) ? length * 4 : SIZE_MAX;
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}
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free(buffer);
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free(result);
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return NULL;
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#else /* !HAVE_FUNCTION_R */
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/* No reentrant function.
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* Duplicate the structure to avoid other call to overwrite it.
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*
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* We should also restore the initial structure. But that would be
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* overkill.
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*/
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LOOKUP_TYPE *result = FUNCTION_NAME(ARG_NAME);
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if (result) {
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result = DUP_FUNCTION(result);
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if (NULL == result) {
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goto oom;
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}
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}
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return result;
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#endif
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oom:
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fprintf (log_get_logfd(), _("%s: out of memory\n"),
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"x" STRINGIZE(FUNCTION_NAME));
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exit (13);
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}
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