include/qapi/error.h

   1 /*
   2  * QEMU Error Objects
   3  *
   4  * Copyright IBM, Corp. 2011
   5  * Copyright (C) 2011-2015 Red Hat, Inc.
   6  *
   7  * Authors:
   8  *  Anthony Liguori   <aliguori@us.ibm.com>
   9  *  Markus Armbruster <armbru@redhat.com>
  10  *
  11  * This work is licensed under the terms of the GNU LGPL, version 2.  See
  12  * the COPYING.LIB file in the top-level directory.
  13  */
  14
  15 /*
  16  * Error reporting system loosely patterned after Glib's GError.
  17  *
  18  * Create an error:
  19  *     error_setg(&err, "situation normal, all fouled up");
  20  *
  21  * Report an error to stderr:
  22  *     error_report_err(err);
  23  * This frees the error object.
  24  *
  25  * Report an error somewhere else:
  26  *     const char *msg = error_get_pretty(err);
  27  *     do with msg what needs to be done...
  28  *     error_free(err);
  29  *
  30  * Handle an error without reporting it (just for completeness):
  31  *     error_free(err);
  32  *
  33  * Assert that an expected error occurred, but clean it up without
  34  * reporting it (primarily useful in testsuites):
  35  *     error_free_or_abort(&err);
  36  *
  37  * Pass an existing error to the caller:
  38  *     error_propagate(errp, err);
  39  * where Error **errp is a parameter, by convention the last one.
  40  *
  41  * Create a new error and pass it to the caller:
  42  *     error_setg(errp, "situation normal, all fouled up");
  43  *
  44  * Call a function and receive an error from it:
  45  *     Error *err = NULL;
  46  *     foo(arg, &err);
  47  *     if (err) {
  48  *         handle the error...
  49  *     }
  50  *
  51  * Call a function ignoring errors:
  52  *     foo(arg, NULL);
  53  *
  54  * Call a function aborting on errors:
  55  *     foo(arg, &error_abort);
  56  *
  57  * Call a function treating errors as fatal:
  58  *     foo(arg, &error_fatal);
  59  *
  60  * Receive an error and pass it on to the caller:
  61  *     Error *err = NULL;
  62  *     foo(arg, &err);
  63  *     if (err) {
  64  *         handle the error...
  65  *         error_propagate(errp, err);
  66  *     }
  67  * where Error **errp is a parameter, by convention the last one.
  68  *
  69  * Do *not* "optimize" this to
  70  *     foo(arg, errp);
  71  *     if (*errp) { // WRONG!
  72  *         handle the error...
  73  *     }
  74  * because errp may be NULL!
  75  *
  76  * But when all you do with the error is pass it on, please use
  77  *     foo(arg, errp);
  78  * for readability.
  79  */
  80
  81 #ifndef ERROR_H
  82 #define ERROR_H
  83
  84 #include "qemu/compiler.h"
  85 #include "qapi-types.h"
  86 #include <stdbool.h>
  87
  88 /*
  89  * Opaque error object.
  90  */
  91 typedef struct Error Error;
  92
  93 /*
  94  * Get @err's human-readable error message.
  95  */
  96 const char *error_get_pretty(Error *err);
  97
  98 /*
  99  * Get @err's error class.
 100  * Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
 101  * strongly discouraged.
 102  */
 103 ErrorClass error_get_class(const Error *err);
 104
 105 /*
 106  * Create a new error object and assign it to *@errp.
 107  * If @errp is NULL, the error is ignored.  Don't bother creating one
 108  * then.
 109  * If @errp is &error_abort, print a suitable message and abort().
 110  * If @errp is &error_fatal, print a suitable message and exit(1).
 111  * If @errp is anything else, *@errp must be NULL.
 112  * The new error's class is ERROR_CLASS_GENERIC_ERROR, and its
 113  * human-readable error message is made from printf-style @fmt, ...
 114  */
 115 #define error_setg(errp, fmt, ...)                              \
 116     error_setg_internal((errp), __FILE__, __LINE__, __func__,   \
 117                         (fmt), ## __VA_ARGS__)
 118 void error_setg_internal(Error **errp,
 119                          const char *src, int line, const char *func,
 120                          const char *fmt, ...)
 121     GCC_FMT_ATTR(5, 6);
 122
 123 /*
 124  * Just like error_setg(), with @os_error info added to the message.
 125  * If @os_error is non-zero, ": " + strerror(os_error) is appended to
 126  * the human-readable error message.
 127  */
 128 #define error_setg_errno(errp, os_error, fmt, ...)                      \
 129     error_setg_errno_internal((errp), __FILE__, __LINE__, __func__,     \
 130                               (os_error), (fmt), ## __VA_ARGS__)
 131 void error_setg_errno_internal(Error **errp,
 132                                const char *fname, int line, const char *func,
 133                                int os_error, const char *fmt, ...)
 134     GCC_FMT_ATTR(6, 7);
 135
 136 #ifdef _WIN32
 137 /*
 138  * Just like error_setg(), with @win32_error info added to the message.
 139  * If @win32_error is non-zero, ": " + g_win32_error_message(win32_err)
 140  * is appended to the human-readable error message.
 141  */
 142 #define error_setg_win32(errp, win32_err, fmt, ...)                     \
 143     error_setg_win32_internal((errp), __FILE__, __LINE__, __func__,     \
 144                               (win32_err), (fmt), ## __VA_ARGS__)
 145 void error_setg_win32_internal(Error **errp,
 146                                const char *src, int line, const char *func,
 147                                int win32_err, const char *fmt, ...)
 148     GCC_FMT_ATTR(6, 7);
 149 #endif
 150
 151 /*
 152  * Propagate error object (if any) from @local_err to @dst_errp.
 153  * If @local_err is NULL, do nothing (because there's nothing to
 154  * propagate).
 155  * Else, if @dst_errp is NULL, errors are being ignored.  Free the
 156  * error object.
 157  * Else, if @dst_errp is &error_abort, print a suitable message and
 158  * abort().
 159  * Else, if @dst_errp is &error_fatal, print a suitable message and
 160  * exit(1).
 161  * Else, if @dst_errp already contains an error, ignore this one: free
 162  * the error object.
 163  * Else, move the error object from @local_err to *@dst_errp.
 164  * On return, @local_err is invalid.
 165  */
 166 void error_propagate(Error **dst_errp, Error *local_err);
 167
 168 /**
 169  * Append a printf-style human-readable explanation to an existing error.
 170  * May be called multiple times, and safe if @errp is NULL.
 171  */
 172 void error_append_hint(Error **errp, const char *fmt, ...)
 173     GCC_FMT_ATTR(2, 3);
 174
 175 /*
 176  * Convenience function to report open() failure.
 177  */
 178 #define error_setg_file_open(errp, os_errno, filename)                  \
 179     error_setg_file_open_internal((errp), __FILE__, __LINE__, __func__, \
 180                                   (os_errno), (filename))
 181 void error_setg_file_open_internal(Error **errp,
 182                                    const char *src, int line, const char *func,
 183                                    int os_errno, const char *filename);
 184
 185 /*
 186  * Return an exact copy of @err.
 187  */
 188 Error *error_copy(const Error *err);
 189
 190 /*
 191  * Free @err.
 192  * @err may be NULL.
 193  */
 194 void error_free(Error *err);
 195
 196 /*
 197  * Convenience function to assert that *@errp is set, then silently free it.
 198  */
 199 void error_free_or_abort(Error **errp);
 200
 201 /*
 202  * Convenience function to error_report() and free @err.
 203  */
 204 void error_report_err(Error *);
 205
 206 /*
 207  * Just like error_setg(), except you get to specify the error class.
 208  * Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
 209  * strongly discouraged.
 210  */
 211 #define error_set(errp, err_class, fmt, ...)                    \
 212     error_set_internal((errp), __FILE__, __LINE__, __func__,    \
 213                        (err_class), (fmt), ## __VA_ARGS__)
 214 void error_set_internal(Error **errp,
 215                         const char *src, int line, const char *func,
 216                         ErrorClass err_class, const char *fmt, ...)
 217     GCC_FMT_ATTR(6, 7);
 218
 219 /*
 220  * Pass to error_setg() & friends to abort() on error.
 221  */
 222 extern Error *error_abort;
 223
 224 /*
 225  * Pass to error_setg() & friends to exit(1) on error.
 226  */
 227 extern Error *error_fatal;
 228
 229 #endif