gecko-dev/mfbt/tests/TestMacroArgs.cpp
Mike Hommey 38a6de0fe3 Bug 1369622 - Fix MOZ_FOR_EACH with an empty list. r=froydnj
I'm not sure how I tested MOZ_FOR_EACH in bug 1368932, but it turns out
it doesn't work with an empty list, despite
MOZ_PASTE_PREFIX_AND_ARG_COUNT now supporting 0 arguments.

Macros can be tricky, and it ends up being easier to make things work
cross-compiler with a separate macro that does the counting, and
(re)building MOZ_PASTE_PREFIX_AND_ARG_COUNT on top of that. Then
MOZ_FOR_EACH ends up working as expected with an empty list.

So this adds a MOZ_ARG_COUNT macro that counts the number of variadic
arguments it's given, and derives MOZ_PASTE_PREFIX_AND_ARG_COUNT from
it.

And this adds a testcase validating that MOZ_FOR_EACH works properly
with an empty list as a result.

--HG--
extra : rebase_source : 309371d87bd1561fbd2153f44fc1256185045d23
2017-06-02 14:53:54 +09:00

37 lines
1.4 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "mozilla/MacroArgs.h"
static_assert(MOZ_ARG_COUNT() == 0, "");
static_assert(MOZ_ARG_COUNT(a) == 1, "");
static_assert(MOZ_ARG_COUNT(a, b) == 2, "");
static_assert(MOZ_ARG_COUNT(a, b, c) == 3, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(100) == 1000, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(100, a) == 1001, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(100, a, b) == 1002, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(100, a, b, c) == 1003, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, a, b, c) == 3, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, a) == 1, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, !a) == 1, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, (a, b)) == 1, "");
static_assert(MOZ_PASTE_PREFIX_AND_ARG_COUNT(, MOZ_ARGS_AFTER_1(a, b, c)) == 2,
"MOZ_ARGS_AFTER_1(a, b, c) should expand to 'b, c'");
static_assert(MOZ_ARGS_AFTER_2(a, b, 3) == 3,
"MOZ_ARGS_AFTER_2(a, b, 3) should expand to '3'");
static_assert(MOZ_ARG_1(10, 20, 30) == 10, "");
static_assert(MOZ_ARG_2(10, 20, 30) == 20, "");
int
main()
{
return 0;
}