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2bf7921c7e
This commit converts the license handling to adhere to the REUSE
specification. It specifically:
1. Adds used licnses to LICENSES/ directory
2. Add "isc" template for adding the copyright boilerplate
3. Changes all source files to include copyright and SPDX license
header, this includes all the C sources, documentation, zone files,
configuration files. There are notes in the doc/dev/copyrights file
on how to add correct headers to the new files.
4. Handle the rest that can't be modified via .reuse/dep5 file. The
binary (or otherwise unmodifiable) files could have license places
next to them in <foo>.license file, but this would lead to cluttered
repository and most of the files handled in the .reuse/dep5 file are
system test files.
(cherry picked from commit 58bd26b6cf)
72 lines
2.2 KiB
Text
72 lines
2.2 KiB
Text
<!--
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Copyright (C) Internet Systems Consortium, Inc. ("ISC")
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SPDX-License-Identifier: MPL-2.0
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This Source Code Form is subject to the terms of the Mozilla Public
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License, v. 2.0. If a copy of the MPL was not distributed with this
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file, you can obtain one at https://mozilla.org/MPL/2.0/.
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See the COPYRIGHT file distributed with this work for additional
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information regarding copyright ownership.
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-->
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Magic Numbers
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A number of data structures in the ISC and DNS libraries have an unsigned int
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magic number as the first field. The purpose of the magic number is
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principally to validate that a pointer a subroutine has gotten really points
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to the type it claims to be. This helps detect problems caused by resources
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being freed prematurely, that have been corrupted, or that have not been
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properly initialized. It can also be handy in debugging.
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Magic numbers should always be the first field. They never require locking
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to access. As to the actual value to be used, something mnemonic is good:
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#define TASK_MAGIC 0x5441534BU /* TASK. */
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#define VALID_TASK(t) ((t) != NULL && \
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(t)->magic == TASK_MAGIC)
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#define TASK_MANAGER_MAGIC 0x54534B4DU /* TSKM. */
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#define VALID_MANAGER(m) ((m) != NULL && \
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(m)->magic ==
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TASK_MANAGER_MAGIC)
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Unless the memory cost is critical, most objects should have a magic number.
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The magic number should be the last field set in a creation routine, so that
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an object will never be stamped with a magic number unless it is valid.
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The magic number should be set to zero immediately before the object is
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freed.
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Magic values are generally private to the implementation of the type. I.e.
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they are defined in the .c file, not the .h file.
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Validation of magic numbers is done by routines that manipulate the type,
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not by users of the type. Indeed, user validation is usually not possible
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because the magic number is not public.
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Magic number checking may become a build option in a future release. E.g.
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struct foo {
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ISC_MAGIC_DECLARATION
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/* ... */
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}
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foo_create() {
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/* ... */
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ISC_MAGIC_SET(value);
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}
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foo_destroy() {
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/* ... */
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ISC_MAGIC_CLEAR(value);
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}
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#define FOO_MAGIC 0x00010203U
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#define VALID_FOO(f) ISC_MAGIC_VALIDATE(f, FOO_MAGIC)
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foo_dosomething(foo *f) {
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REQUIRE(VALID_FOO(f));
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}
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