#### 3.2.1 Error Values

Data type: gcry_err_code_t ¶

  The `gcry_err_code_t` type is an alias for the `libgpg-error` type `gpg_err_code_t`. The error code indicates the type of an error, or the reason why an operation failed.

  A list of important error codes can be found in the next section.

Data type: gcry_err_source_t ¶

  The `gcry_err_source_t` type is an alias for the `libgpg-error` type `gpg_err_source_t`. The error source has not a precisely defined meaning. Sometimes it is the place where the error happened, sometimes it is the place where an error was encoded into an error value. Usually the error source will give an indication to where to look for the problem. This is not always true, but it is attempted to achieve this goal.

  A list of important error sources can be found in the next section.

Data type: gcry_error_t ¶

  The `gcry_error_t` type is an alias for the `libgpg-error` type `gpg_error_t`. An error value like this has always two components, an error code and an error source. Both together form the error value.

  Thus, the error value can not be directly compared against an error code, but the accessor functions described below must be used. However, it is guaranteed that only 0 is used to indicate success (`GPG_ERR_NO_ERROR`), and that in this case all other parts of the error value are set to 0, too.

  Note that in Libgcrypt, the error source is used purely for diagnostic purposes. Only the error code should be checked to test for a certain outcome of a function. The manual only documents the error code part of an error value. The error source is left unspecified and might be anything.

Function: gcry_err_code_t gcry_err_code (gcry_error_t err) ¶

  The static inline function `gcry_err_code` returns the `gcry_err_code_t` component of the error value err. This function must be used to extract the error code from an error value in order to compare it with the `GPG_ERR_*` error code macros.

Function: gcry_err_source_t gcry_err_source (gcry_error_t err) ¶

  The static inline function `gcry_err_source` returns the `gcry_err_source_t` component of the error value err. This function must be used to extract the error source from an error value in order to compare it with the `GPG_ERR_SOURCE_*` error source macros.

Function: gcry_error_t gcry_err_make (gcry_err_source_t source, gcry_err_code_t code) ¶

  The static inline function `gcry_err_make` returns the error value consisting of the error source source and the error code code.

  This function can be used in callback functions to construct an error value to return it to the library.

Function: gcry_error_t gcry_error (gcry_err_code_t code) ¶

  The static inline function `gcry_error` returns the error value consisting of the default error source and the error code code.

  For GCRY applications, the default error source is `GPG_ERR_SOURCE_USER_1`. You can define `GCRY_ERR_SOURCE_DEFAULT` before including `gcrypt.h` to change this default.

  This function can be used in callback functions to construct an error value to return it to the library.

The `libgpg-error` library provides error codes for all system error numbers it knows about. If err is an unknown error number, the error code `GPG_ERR_UNKNOWN_ERRNO` is used. The following functions can be used to construct error values from system errno numbers.

Function: gcry_error_t gcry_err_make_from_errno (gcry_err_source_t source, int err) ¶

  The function `gcry_err_make_from_errno` is like `gcry_err_make`, but it takes a system error like `errno` instead of a `gcry_err_code_t` error code.

Function: gcry_error_t gcry_error_from_errno (int err) ¶

  The function `gcry_error_from_errno` is like `gcry_error`, but it takes a system error like `errno` instead of a `gcry_err_code_t` error code.

Sometimes you might want to map system error numbers to error codes directly, or map an error code representing a system error back to the system error number. The following functions can be used to do that.

Function: gcry_err_code_t gcry_err_code_from_errno (int err) ¶

  The function `gcry_err_code_from_errno` returns the error code for the system error err. If err is not a known system error, the function returns `GPG_ERR_UNKNOWN_ERRNO`.

Function: int gcry_err_code_to_errno (gcry_err_code_t err) ¶

  The function `gcry_err_code_to_errno` returns the system error for the error code err. If err is not an error code representing a system error, or if this system error is not defined on this system, the function returns `0`.