error: Revamp interface documentation
Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
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Markus Armbruster
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@ -2,13 +2,75 @@
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* QEMU Error Objects
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*
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* Copyright IBM, Corp. 2011
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* Copyright (C) 2011-2015 Red Hat, Inc.
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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* Markus Armbruster <armbru@redhat.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2. See
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* the COPYING.LIB file in the top-level directory.
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*/
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/*
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* Error reporting system loosely patterned after Glib's GError.
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*
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* Create an error:
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* error_setg(&err, "situation normal, all fouled up");
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*
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* Report an error to stderr:
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* error_report_err(err);
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* This frees the error object.
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*
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* Report an error somewhere else:
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* const char *msg = error_get_pretty(err);
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* do with msg what needs to be done...
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* error_free(err);
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*
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* Handle an error without reporting it (just for completeness):
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* error_free(err);
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*
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* Pass an existing error to the caller:
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* error_propagate(errp, err);
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* where Error **errp is a parameter, by convention the last one.
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*
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* Create a new error and pass it to the caller:
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* error_setg(errp, "situation normal, all fouled up");
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*
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* Call a function and receive an error from it:
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* Error *err = NULL;
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* foo(arg, &err);
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* if (err) {
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* handle the error...
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* }
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*
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* Call a function ignoring errors:
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* foo(arg, NULL);
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*
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* Call a function aborting on errors:
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* foo(arg, &error_abort);
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*
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* Receive an error and pass it on to the caller:
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* Error *err = NULL;
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* foo(arg, &err);
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* if (err) {
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* handle the error...
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* error_propagate(errp, err);
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* }
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* where Error **errp is a parameter, by convention the last one.
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*
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* Do *not* "optimize" this to
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* foo(arg, errp);
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* if (*errp) { // WRONG!
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* handle the error...
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* }
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* because errp may be NULL!
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*
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* But when all you do with the error is pass it on, please use
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* foo(arg, errp);
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* for readability.
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*/
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#ifndef ERROR_H
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#define ERROR_H
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@ -16,85 +78,100 @@
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#include "qapi-types.h"
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#include <stdbool.h>
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/**
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* A class representing internal errors within QEMU. An error has a ErrorClass
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* code and a human message.
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/*
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* Opaque error object.
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*/
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typedef struct Error Error;
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/**
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* Set an indirect pointer to an error given a ErrorClass value and a
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* printf-style human message. This function is not meant to be used outside
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* of QEMU.
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/*
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* Get @err's human-readable error message.
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*/
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void error_set(Error **errp, ErrorClass err_class, const char *fmt, ...)
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GCC_FMT_ATTR(3, 4);
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const char *error_get_pretty(Error *err);
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/**
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* Set an indirect pointer to an error given a ErrorClass value and a
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* printf-style human message, followed by a strerror() string if
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* @os_error is not zero.
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/*
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* Get @err's error class.
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* Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
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* strongly discouraged.
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*/
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ErrorClass error_get_class(const Error *err);
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/*
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* Create a new error object and assign it to *@errp.
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* If @errp is NULL, the error is ignored. Don't bother creating one
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* then.
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* If @errp is &error_abort, print a suitable message and abort().
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* If @errp is anything else, *@errp must be NULL.
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* The new error's class is ERROR_CLASS_GENERIC_ERROR, and its
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* human-readable error message is made from printf-style @fmt, ...
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*/
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void error_setg(Error **errp, const char *fmt, ...)
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GCC_FMT_ATTR(2, 3);
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/*
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* Just like error_setg(), with @os_error info added to the message.
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* If @os_error is non-zero, ": " + strerror(os_error) is appended to
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* the human-readable error message.
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*/
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void error_setg_errno(Error **errp, int os_error, const char *fmt, ...)
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GCC_FMT_ATTR(3, 4);
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#ifdef _WIN32
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/**
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* Set an indirect pointer to an error given a ErrorClass value and a
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* printf-style human message, followed by a g_win32_error_message() string if
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* @win32_err is not zero.
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/*
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* Just like error_setg(), with @win32_error info added to the message.
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* If @win32_error is non-zero, ": " + g_win32_error_message(win32_err)
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* is appended to the human-readable error message.
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*/
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void error_setg_win32(Error **errp, int win32_err, const char *fmt, ...)
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GCC_FMT_ATTR(3, 4);
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#endif
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/**
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* Same as error_set(), but sets a generic error
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/*
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* Propagate error object (if any) from @local_err to @dst_errp.
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* If @local_err is NULL, do nothing (because there's nothing to
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* propagate).
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* Else, if @dst_errp is NULL, errors are being ignored. Free the
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* error object.
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* Else, if @dst_errp is &error_abort, print a suitable message and
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* abort().
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* Else, if @dst_errp already contains an error, ignore this one: free
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* the error object.
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* Else, move the error object from @local_err to *@dst_errp.
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* On return, @local_err is invalid.
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*/
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void error_setg(Error **errp, const char *fmt, ...)
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GCC_FMT_ATTR(2, 3);
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void error_propagate(Error **dst_errp, Error *local_err);
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/**
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* Helper for open() errors
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/*
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* Convenience function to report open() failure.
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*/
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void error_setg_file_open(Error **errp, int os_errno, const char *filename);
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/*
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* Get the error class of an error object.
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*/
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ErrorClass error_get_class(const Error *err);
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/**
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* Returns an exact copy of the error passed as an argument.
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* Return an exact copy of @err.
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*/
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Error *error_copy(const Error *err);
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/**
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* Get a human readable representation of an error object.
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*/
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const char *error_get_pretty(Error *err);
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/**
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* Convenience function to error_report() and free an error object.
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*/
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void error_report_err(Error *);
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/**
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* Propagate an error to an indirect pointer to an error. This function will
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* always transfer ownership of the error reference and handles the case where
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* dst_err is NULL correctly. Errors after the first are discarded.
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*/
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void error_propagate(Error **dst_errp, Error *local_err);
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/**
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* Free an error object.
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/*
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* Free @err.
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* @err may be NULL.
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*/
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void error_free(Error *err);
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/**
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* If passed to error_set and friends, abort().
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/*
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* Convenience function to error_report() and free @err.
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*/
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void error_report_err(Error *);
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/*
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* Just like error_setg(), except you get to specify the error class.
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* Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
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* strongly discouraged.
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*/
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void error_set(Error **errp, ErrorClass err_class, const char *fmt, ...)
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GCC_FMT_ATTR(3, 4);
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/*
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* Pass to error_setg() & friends to abort() on error.
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*/
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extern Error *error_abort;
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#endif
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