From 06d47e2efe1387a3873529c52a4c7c680ddeee22 Mon Sep 17 00:00:00 2001 From: "Richard W.M. Jones" Date: Thu, 7 Jul 2022 12:37:10 +0100 Subject: [PATCH] common/include: Add ARRAY_SIZE macro This macro returns the length (in elements) at compile time of arrays declared as: int foo[] = { 1, 2, 3 }; ARRAY_SIZE(foo) ===> 3 It also attempts to detect some errors, such as using the macro with a pointer instead of an array, with some ideas borrowed (not copied) from Linux, QEMU and Stack Overflow questions. Link: https://stackoverflow.com/questions/19452971/array-size-macro-that-rejects-pointers Link: https://listman.redhat.com/archives/libguestfs/2022-July/029412.html Thanks: Laszlo Ersek (cherry picked from commit 0fa23df5cd5dc97a55857416ea81d5de6d867c18) --- .gitignore | 1 + common/include/Makefile.am | 7 +++ common/include/array-size.h | 41 +++++++++++++ common/include/compiler-macros.h | 60 +++++++++++++++++++ common/include/test-array-size.c | 100 +++++++++++++++++++++++++++++++ 5 files changed, 209 insertions(+) create mode 100644 common/include/array-size.h create mode 100644 common/include/compiler-macros.h create mode 100644 common/include/test-array-size.c diff --git a/.gitignore b/.gitignore index 10e1f99d..658fd4e6 100644 --- a/.gitignore +++ b/.gitignore @@ -35,6 +35,7 @@ plugins/*/*.3 /aclocal.m4 /autom4te.cache /common/bitmap/test-bitmap +/common/include/test-array-size /common/include/test-ascii-ctype /common/include/test-ascii-string /common/include/test-byte-swapping diff --git a/common/include/Makefile.am b/common/include/Makefile.am index b73dd471..d3cf9408 100644 --- a/common/include/Makefile.am +++ b/common/include/Makefile.am @@ -34,10 +34,12 @@ include $(top_srcdir)/common-rules.mk # These headers contain only common code shared by the core server, # plugins and/or filters. They are not installed. EXTRA_DIST = \ + array-size.h \ ascii-ctype.h \ ascii-string.h \ byte-swapping.h \ checked-overflow.h \ + compiler-macros.h \ exit-with-parent.h \ hexdigit.h \ isaligned.h \ @@ -55,6 +57,7 @@ EXTRA_DIST = \ # Unit tests. TESTS = \ + test-array-size \ test-ascii-ctype \ test-ascii-string \ test-byte-swapping \ @@ -69,6 +72,10 @@ TESTS = \ $(NULL) check_PROGRAMS = $(TESTS) +test_array_size_SOURCES = test-array-size.c array-size.h +test_array_size_CPPFLAGS = -I$(srcdir) +test_array_size_CFLAGS = $(WARNINGS_CFLAGS) + test_ascii_ctype_SOURCES = test-ascii-ctype.c ascii-ctype.h test_ascii_ctype_CPPFLAGS = -I$(srcdir) test_ascii_ctype_CFLAGS = $(WARNINGS_CFLAGS) diff --git a/common/include/array-size.h b/common/include/array-size.h new file mode 100644 index 00000000..b6d33dde --- /dev/null +++ b/common/include/array-size.h @@ -0,0 +1,41 @@ +/* nbdkit + * Copyright (C) 2013-2022 Red Hat Inc. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef NBDKIT_ARRAY_SIZE_H +#define NBDKIT_ARRAY_SIZE_H + +#include "compiler-macros.h" + +#define ARRAY_SIZE(a) \ + ((sizeof (a) / sizeof ((a)[0])) + BUILD_BUG_ON_ZERO (!TYPE_IS_ARRAY(a))) + +#endif /* NBDKIT_ARRAY_SIZE_H */ diff --git a/common/include/compiler-macros.h b/common/include/compiler-macros.h new file mode 100644 index 00000000..504e0085 --- /dev/null +++ b/common/include/compiler-macros.h @@ -0,0 +1,60 @@ +/* nbdkit + * Copyright (C) 2013-2022 Red Hat Inc. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#ifndef NBDKIT_COMPILER_MACROS_H +#define NBDKIT_COMPILER_MACROS_H + +#ifndef __cplusplus + +/* This expression fails at compile time if 'expr' is true. It does + * this by constructing a struct which has an impossible + * (negative-sized) array. + * + * If 'expr' is false then we subtract the sizes of the two identical + * structures, returning zero. + */ +#define BUILD_BUG_ON_ZERO_SIZEOF(expr) \ + (sizeof (struct { int _array_size_failed[(expr) ? -1 : 1]; })) +#define BUILD_BUG_ON_ZERO(expr) \ + (BUILD_BUG_ON_ZERO_SIZEOF(expr) - BUILD_BUG_ON_ZERO_SIZEOF(expr)) + +#define TYPE_IS_ARRAY(a) \ + (!__builtin_types_compatible_p (typeof (a), typeof (&(a)[0]))) + +#else /* __cplusplus */ + +#define BUILD_BUG_ON_ZERO(expr) 0 +#define TYPE_IS_ARRAY(a) 1 + +#endif /* __cplusplus */ + +#endif /* NBDKIT_COMPILER_MACROS_H */ diff --git a/common/include/test-array-size.c b/common/include/test-array-size.c new file mode 100644 index 00000000..d77ba3c9 --- /dev/null +++ b/common/include/test-array-size.c @@ -0,0 +1,100 @@ +/* nbdkit + * Copyright (C) 2020-2022 Red Hat Inc. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * * Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * * Neither the name of Red Hat nor the names of its contributors may be + * used to endorse or promote products derived from this software without + * specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#include + +#include +#include +#undef NDEBUG /* Keep test strong even for nbdkit built without assertions */ +#include + +#include "array-size.h" + +struct st { const char *s; int i; }; + +static const char *s0[] = { }; +static const char *s1[] = { "a" }; +static const char *s3[] = { "a", "b", "c" }; +static const char *s4[4] = { "a", "b", "c", "d" }; +static int i0[] = { }; +static int i1[] = { 1 }; +static int i3[] = { 1, 2, 3 }; +static int i4[4] = { 1, 2, 3, 4 }; +static struct st st0[] = { }; +static struct st st1[] = { { "a", 1 } }; +static struct st st3[] = { { "a", 1 }, { "b", 2 }, { "c", 3 } }; +static struct st st4[4] = { { "a", 1 }, { "b", 2 }, { "c", 3 }, { "d", 4 } }; +static struct st st4_0[4]; + +int +main (void) +{ + assert (ARRAY_SIZE (s0) == 0); + assert (ARRAY_SIZE (s1) == 1); + assert (ARRAY_SIZE (s3) == 3); + assert (ARRAY_SIZE (s4) == 4); + assert (ARRAY_SIZE (i0) == 0); + assert (ARRAY_SIZE (i1) == 1); + assert (ARRAY_SIZE (i3) == 3); + assert (ARRAY_SIZE (i4) == 4); + assert (ARRAY_SIZE (st0) == 0); + assert (ARRAY_SIZE (st1) == 1); + assert (ARRAY_SIZE (st3) == 3); + assert (ARRAY_SIZE (st4) == 4); + assert (ARRAY_SIZE (st4_0) == 4); + +#ifdef static_assert + static_assert (ARRAY_SIZE (s0) == 0, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (s1) == 1, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (s3) == 3, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (s4) == 4, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (i0) == 0, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (i1) == 1, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (i3) == 3, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (i4) == 4, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (st0) == 0, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (st1) == 1, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (st3) == 3, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (st4) == 4, "ARRAY_SIZE macro does not work"); + static_assert (ARRAY_SIZE (st4_0) == 4, "ARRAY_SIZE macro does not work"); +#endif + + /* You can uncomment this to test the negative case. Unfortunately + * it's difficult to automate this test. + */ +#if 0 + int *p = i4; + assert (ARRAY_SIZE (p) == 4); +#endif + + exit (EXIT_SUCCESS); +} -- 2.31.1