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  * Pass an existing error to the caller:
  34  *     error_propagate(errp, err);
  35  * where Error **errp is a parameter, by convention the last one.
  36  *
  37  * Create a new error and pass it to the caller:
  38  *     error_setg(errp, "situation normal, all fouled up");
  39  *
  40  * Call a function and receive an error from it:
  41  *     Error *err = NULL;
  42  *     foo(arg, &err);
  43  *     if (err) {
  44  *         handle the error...
  45  *     }
  46  *
  47  * Call a function ignoring errors:
  48  *     foo(arg, NULL);
  49  *
  50  * Call a function aborting on errors:
  51  *     foo(arg, &error_abort);
  52  *
  53  * Call a function treating errors as fatal:
  54  *     foo(arg, &error_fatal);
  55  *
  56  * Receive an error and pass it on to the caller:
  57  *     Error *err = NULL;
  58  *     foo(arg, &err);
  59  *     if (err) {
  60  *         handle the error...
  61  *         error_propagate(errp, err);
  62  *     }
  63  * where Error **errp is a parameter, by convention the last one.
  64  *
  65  * Do *not* "optimize" this to
  66  *     foo(arg, errp);
  67  *     if (*errp) { // WRONG!
  68  *         handle the error...
  69  *     }
  70  * because errp may be NULL!
  71  *
  72  * But when all you do with the error is pass it on, please use
  73  *     foo(arg, errp);
  74  * for readability.
  75  */
  76
  77 #ifndef ERROR_H
  78 #define ERROR_H
  79
  80 #include "qemu/compiler.h"
  81 #include "qapi-types.h"
  82 #include <stdbool.h>
  83
  84 /*
  85  * Opaque error object.
  86  */
  87 typedef struct Error Error;
  88
  89 /*
  90  * Get @err's human-readable error message.
  91  */
  92 const char *error_get_pretty(Error *err);
  93
  94 /*
  95  * Get @err's error class.
  96  * Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
  97  * strongly discouraged.
  98  */
  99 ErrorClass error_get_class(const Error *err);
 100
 101 /*
 102  * Create a new error object and assign it to *@errp.
 103  * If @errp is NULL, the error is ignored.  Don't bother creating one
 104  * then.
 105  * If @errp is &error_abort, print a suitable message and abort().
 106  * If @errp is &error_fatal, print a suitable message and exit(1).
 107  * If @errp is anything else, *@errp must be NULL.
 108  * The new error's class is ERROR_CLASS_GENERIC_ERROR, and its
 109  * human-readable error message is made from printf-style @fmt, ...
 110  */
 111 #define error_setg(errp, fmt, ...)                              \
 112     error_setg_internal((errp), __FILE__, __LINE__, __func__,   \
 113                         (fmt), ## __VA_ARGS__)
 114 void error_setg_internal(Error **errp,
 115                          const char *src, int line, const char *func,
 116                          const char *fmt, ...)
 117     GCC_FMT_ATTR(5, 6);
 118
 119 /*
 120  * Just like error_setg(), with @os_error info added to the message.
 121  * If @os_error is non-zero, ": " + strerror(os_error) is appended to
 122  * the human-readable error message.
 123  */
 124 #define error_setg_errno(errp, os_error, fmt, ...)                      \
 125     error_setg_errno_internal((errp), __FILE__, __LINE__, __func__,     \
 126                               (os_error), (fmt), ## __VA_ARGS__)
 127 void error_setg_errno_internal(Error **errp,
 128                                const char *fname, int line, const char *func,
 129                                int os_error, const char *fmt, ...)
 130     GCC_FMT_ATTR(6, 7);
 131
 132 #ifdef _WIN32
 133 /*
 134  * Just like error_setg(), with @win32_error info added to the message.
 135  * If @win32_error is non-zero, ": " + g_win32_error_message(win32_err)
 136  * is appended to the human-readable error message.
 137  */
 138 #define error_setg_win32(errp, win32_err, fmt, ...)                     \
 139     error_setg_win32_internal((errp), __FILE__, __LINE__, __func__,     \
 140                               (win32_err), (fmt), ## __VA_ARGS__)
 141 void error_setg_win32_internal(Error **errp,
 142                                const char *src, int line, const char *func,
 143                                int win32_err, const char *fmt, ...)
 144     GCC_FMT_ATTR(6, 7);
 145 #endif
 146
 147 /*
 148  * Propagate error object (if any) from @local_err to @dst_errp.
 149  * If @local_err is NULL, do nothing (because there's nothing to
 150  * propagate).
 151  * Else, if @dst_errp is NULL, errors are being ignored.  Free the
 152  * error object.
 153  * Else, if @dst_errp is &error_abort, print a suitable message and
 154  * abort().
 155  * Else, if @dst_errp is &error_fatal, print a suitable message and
 156  * exit(1).
 157  * Else, if @dst_errp already contains an error, ignore this one: free
 158  * the error object.
 159  * Else, move the error object from @local_err to *@dst_errp.
 160  * On return, @local_err is invalid.
 161  */
 162 void error_propagate(Error **dst_errp, Error *local_err);
 163
 164 /**
 165  * Append a printf-style human-readable explanation to an existing error.
 166  * May be called multiple times, and safe if @errp is NULL.
 167  */
 168 void error_append_hint(Error **errp, const char *fmt, ...)
 169     GCC_FMT_ATTR(2, 3);
 170
 171 /*
 172  * Convenience function to report open() failure.
 173  */
 174 #define error_setg_file_open(errp, os_errno, filename)                  \
 175     error_setg_file_open_internal((errp), __FILE__, __LINE__, __func__, \
 176                                   (os_errno), (filename))
 177 void error_setg_file_open_internal(Error **errp,
 178                                    const char *src, int line, const char *func,
 179                                    int os_errno, const char *filename);
 180
 181 /*
 182  * Return an exact copy of @err.
 183  */
 184 Error *error_copy(const Error *err);
 185
 186 /*
 187  * Free @err.
 188  * @err may be NULL.
 189  */
 190 void error_free(Error *err);
 191
 192 /*
 193  * Convenience function to error_report() and free @err.
 194  */
 195 void error_report_err(Error *);
 196
 197 /*
 198  * Just like error_setg(), except you get to specify the error class.
 199  * Note: use of error classes other than ERROR_CLASS_GENERIC_ERROR is
 200  * strongly discouraged.
 201  */
 202 #define error_set(errp, err_class, fmt, ...)                    \
 203     error_set_internal((errp), __FILE__, __LINE__, __func__,    \
 204                        (err_class), (fmt), ## __VA_ARGS__)
 205 void error_set_internal(Error **errp,
 206                         const char *src, int line, const char *func,
 207                         ErrorClass err_class, const char *fmt, ...)
 208     GCC_FMT_ATTR(6, 7);
 209
 210 /*
 211  * Pass to error_setg() & friends to abort() on error.
 212  */
 213 extern Error *error_abort;
 214
 215 /*
 216  * Pass to error_setg() & friends to exit(1) on error.
 217  */
 218 extern Error *error_fatal;
 219
 220 #endif