From 5e03c718f4e7ff13cb6834eda737c269ebed02ad Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 19:04:52 +0200 Subject: Adding upstream version 1.21.3. Signed-off-by: Daniel Baumann --- lib/malloca.c | 113 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) create mode 100644 lib/malloca.c (limited to 'lib/malloca.c') diff --git a/lib/malloca.c b/lib/malloca.c new file mode 100644 index 0000000..e7beaaf --- /dev/null +++ b/lib/malloca.c @@ -0,0 +1,113 @@ +/* Safe automatic memory allocation. + Copyright (C) 2003, 2006-2007, 2009-2022 Free Software Foundation, Inc. + Written by Bruno Haible , 2003, 2018. + + This file 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. + + This file 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 this program. If not, see . */ + +#define _GL_USE_STDLIB_ALLOC 1 +#include + +/* Specification. */ +#include "malloca.h" + +#include "idx.h" +#include "intprops.h" +#include "verify.h" + +/* The speed critical point in this file is freea() applied to an alloca() + result: it must be fast, to match the speed of alloca(). The speed of + mmalloca() and freea() in the other case are not critical, because they + are only invoked for big memory sizes. + Here we use a bit in the address as an indicator, an idea by Ondřej Bílka. + malloca() can return three types of pointers: + - Pointers ≡ 0 mod 2*sa_alignment_max come from stack allocation. + - Pointers ≡ sa_alignment_max mod 2*sa_alignment_max come from heap + allocation. + - NULL comes from a failed heap allocation. */ + +/* Type for holding very small pointer differences. */ +typedef unsigned char small_t; +/* Verify that it is wide enough. */ +verify (2 * sa_alignment_max - 1 <= (small_t) -1); + +void * +mmalloca (size_t n) +{ +#if HAVE_ALLOCA + /* Allocate one more word, used to determine the address to pass to freea(), + and room for the alignment ≡ sa_alignment_max mod 2*sa_alignment_max. */ + uintptr_t alignment2_mask = 2 * sa_alignment_max - 1; + int plus = sizeof (small_t) + alignment2_mask; + idx_t nplus; + if (!INT_ADD_WRAPV (n, plus, &nplus) && !xalloc_oversized (nplus, 1)) + { + char *mem = (char *) malloc (nplus); + + if (mem != NULL) + { + uintptr_t umem = (uintptr_t)mem, umemplus; + /* The INT_ADD_WRAPV avoids signed integer overflow on + theoretical platforms where UINTPTR_MAX <= INT_MAX. */ + INT_ADD_WRAPV (umem, sizeof (small_t) + sa_alignment_max - 1, + &umemplus); + idx_t offset = ((umemplus & ~alignment2_mask) + + sa_alignment_max - umem); + void *vp = mem + offset; + small_t *p = vp; + /* Here p >= mem + sizeof (small_t), + and p <= mem + sizeof (small_t) + 2 * sa_alignment_max - 1 + hence p + n <= mem + nplus. + So, the memory range [p, p+n) lies in the allocated memory range + [mem, mem + nplus). */ + p[-1] = offset; + /* p ≡ sa_alignment_max mod 2*sa_alignment_max. */ + return p; + } + } + /* Out of memory. */ + return NULL; +#else +# if !MALLOC_0_IS_NONNULL + if (n == 0) + n = 1; +# endif + return malloc (n); +#endif +} + +#if HAVE_ALLOCA +void +freea (void *p) +{ + /* Check argument. */ + if ((uintptr_t) p & (sa_alignment_max - 1)) + { + /* p was not the result of a malloca() call. Invalid argument. */ + abort (); + } + /* Determine whether p was a non-NULL pointer returned by mmalloca(). */ + if ((uintptr_t) p & sa_alignment_max) + { + void *mem = (char *) p - ((small_t *) p)[-1]; + free (mem); + } +} +#endif + +/* + * Hey Emacs! + * Local Variables: + * coding: utf-8 + * End: + */ -- cgit v1.2.3