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https://gitlab.isc.org/isc-projects/bind9
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ec50c58f52
Mostly generated automatically with the following semantic patch, except where coccinelle was confused by #ifdef in lib/isc/net.c @@ expression list args; @@ - UNEXPECTED_ERROR(__FILE__, __LINE__, args) + UNEXPECTED_ERROR(args) @@ expression list args; @@ - FATAL_ERROR(__FILE__, __LINE__, args) + FATAL_ERROR(args)
56 lines
2.2 KiB
Plaintext
56 lines
2.2 KiB
Plaintext
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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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Unexpected Errors
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For portability, the ISC and DNS libraries define their own result codes
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instead of using the operating system's. E.g. the ISC library uses
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ISC_R_NOMEMORY instead of the UNIX-specific ENOMEM.
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The ISC and DNS libraries have a common way of looking at errors and
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other non-success results. An "expected" result is something that can
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happen in the ordinary course of using a function, that is not very
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improbable, and that the caller might care to know. For example, a
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function which opens a file must have a way to say "file not found"
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and "permission denied".
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Other kinds of errors are "unexpected". For example, an I/O error
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might occur. When an unexpected error occurs, we want to be able to
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log the information, but we don't want to translate every
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operating-system-specific error code into and ISC_R_ or DNS_R_ code
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because the are too many of them, and they aren't meaningful to
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clients anyway (they're unexpected errors). If we were using a
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language where we could throw an exception, we'd do that. Since we're
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not, we call UNEXPECTED_ERROR(). E.g.
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#include <isc/error.h>
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void foo() {
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if (some_unix_thang() < 0) {
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UNEXPECTED_ERROR("some_unix_thang() failed: %s",
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strerror(errno));
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return (ISC_R_UNEXPECTED);
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}
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}
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The UNEXPECTED error routine may be specified by the calling application. It
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will log the error somehow (e.g. via. syslog, or printing to stderr).
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This method is a compromise. It makes useful error information available,
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but avoids the complexity of a more sophisticated multi-library "error table"
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scheme.
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In the (rare) situation where a library routine encounters a fatal error and
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has no way of reporting the error to the application, the library may call
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FATAL_ERROR(). This will log the problem and then terminate the application.
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