commit 1a6060fa4263d20d3c1ccf29163165126a413957 Author: Taylor R Campbell <campbell+tor@mumble.net> Date: Tue Oct 23 23:53:39 2018 +0000 New macro CTASSERT(condition) to assert condition at compile-time. To get it, use: #include "lib/cc/ctassert.h" --- src/lib/cc/ctassert.h | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++ src/lib/cc/include.am | 1 + 2 files changed, 76 insertions(+) diff --git a/src/lib/cc/ctassert.h b/src/lib/cc/ctassert.h new file mode 100644 index 000000000..7307bca53 --- /dev/null +++ b/src/lib/cc/ctassert.h @@ -0,0 +1,75 @@ +/*- + * Copyright (c) 2018 Taylor R. Campbell + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. 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. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 THE AUTHOR 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. + */ + +/** + * \file ctassert.h + * + * \brief Compile-time assertions: CTASSERT(expression). + */ + +#ifndef TOR_CTASSERT_H +#define TOR_CTASSERT_H + +#include "lib/cc/compat_compiler.h" + +/** + * CTASSERT(expression) + * + * Trigger a compiler error if expression is false. + */ +#if __STDC_VERSION__ >= 201112L + +/* If C11 is available, just use _Static_assert. */ +#define CTASSERT(x) _Static_assert(x, #x) + +#else + +/* + * If C11 is not available, expand __COUNTER__, or __INCLUDE_LEVEL__ + * and __LINE__, or just __LINE__, with an intermediate preprocessor + * macro CTASSERT_EXPN, and then use CTASSERT_DECL to paste the + * expansions together into a unique name. + * + * We use this name as a typedef of an array type with a positive + * length if the assertion is true, and a negative length of the + * assertion is false, which is invalid and hence triggers a compiler + * error. + */ +#if defined(__COUNTER__) +#define CTASSERT(x) CTASSERT_EXPN(x, c, __COUNTER__) +#elif defined(__INCLUDE_LEVEL__) +#define CTASSERT(x) CTASSERT_EXPN(x, __INCLUDE_LEVEL__, __LINE__) +#else +#define CTASSERT(x) CTASSERT_EXPN(x, l, __LINE__) /* hope it's unique enough */ +#endif + +#define CTASSERT_EXPN(x, a, b) CTASSERT_DECL(x, a, b) +#define CTASSERT_DECL(x, a, b) \ + typedef char tor_ctassert_##a##_##b[(x) ? 1 : -1] ATTR_UNUSED + +#endif + +#endif /* !defined(TOR_CTASSERT_H) */ diff --git a/src/lib/cc/include.am b/src/lib/cc/include.am index 2ae90f97d..52cf8a9f7 100644 --- a/src/lib/cc/include.am +++ b/src/lib/cc/include.am @@ -1,4 +1,5 @@ noinst_HEADERS += \ src/lib/cc/compat_compiler.h \ + src/lib/cc/ctassert.h \ src/lib/cc/torint.h