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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)
41 lines
1.7 KiB
Text
41 lines
1.7 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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Design By Contract
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BIND 9 uses the "Design by Contract" idea for most function calls.
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A quick summary of the idea is that a function and its caller make a
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contract. If the caller meets certain preconditions, then the
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function promises to either fulfill its contract (i.e. guarantee a set
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of postconditions), or to clearly fail.
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"Clearly fail" means that if the function cannot succeed, then it will
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not silently fail and return a value which the caller might interpret
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as success.
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If a caller doesn't meet the preconditions, then "further execution is
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undefined". The function can crash, compute a garbage result, fail silently,
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etc. Allowing the function to define preconditions greatly simplifies many
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APIs, because the API need not have a way of saying "hey caller, the values
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you passed in are garbage".
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Typically, preconditions are specified in the functions .h file, and encoded
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in its body with REQUIRE statements. The REQUIRE statements cause the program
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to dump core if they are not true, and can be used to identify callers that
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are not meeting their preconditions.
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Postconditions can be encoded with ENSURE statements. Within the body of
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a function, INSIST is used to assert that a particular expression must be
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true. Assertions must not have side effects that the function relies upon,
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because assertion checking can be turned off.
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