err - Error codes
#include <openssl/err.h>
unsigned long ERR_get_error(
void ); unsigned long ERR_peek_error(
void ); unsigned long ERR_get_error_line(
const char **file,
int *line ); unsigned long ERR_peek_error_line(
const char **file,
int *line ); unsigned long
ERR_get_error_line_data(
const char **file,
int *line,
const char **data,
int *flags ); unsigned long
ERR_peek_error_line_data(
const char **file,
int *line,
const char **data,
int *flags ); int ERR_GET_LIB(
unsigned long e ); int ERR_GET_FUNC(
unsigned long e ); int ERR_GET_REASON(
unsigned long e ); void ERR_clear_error(
void ); char *ERR_error_string(
unsigned long e,
char *buf ); const char*ERR_lib_error_string(
unsigned long e ); const
char*ERR_func_error_string(
unsigned long e ); const char*ERR_reason_error_string(
unsigned long e ); void ERR_print_errors(
BIO *bp ); void ERR_print_errors_fp(
FILE *fp ); void ERR_load_crypto_strings(
void ); void ERR_free_strings(
void ); void ERR_remove_state(
unsigned long pid ); void ERR_put_error(
int lib,
int func,
int reason,
const char *file,
int line ); void ERR_add_error_data(
int num, ... ); void ERR_load_strings(
int lib,
ERR_STRING_DATA str[] ); unsigned long ERR_PACK(
int lib,
int func,
int reason ); int ERR_get_next_error_library(
void );
When a call to the OpenSSL library fails, this is usually
signalled by the return value, and an error code is stored
in an error queue associated with the current thread. The
err library provides functions to obtain these error codes
and textual error messages.
The ERR_get_error(3) reference page describes how to
access error codes.
Error codes contain information about where the error
occurred, and what went wrong. The ERR_GET_LIB(3) reference
page describes how to extract this information. A
method to obtain human-readable error messages is
described in ERR_error_string(3).
The ERR_clear_error() function can be used to clear the
error queue.
The ERR_remove_state() function should be used to avoid
memory leaks when threads are terminated.
See ERR_put_error(3) if you want to record error codes in
the OpenSSL error system from within your application.
The remainder of this section explains how to add new
error codes to OpenSSL or add error codes from external
libraries.
Reporting errors [Toc] [Back]
Each sublibrary has a specific macro, XXXerr(), that is
used to report errors. Its first argument is a function
code, XXX_F_..., and the second argument is a reason code,
XXX_R_.... Function codes are derived from the function
names; reason codes consist of textual error descriptions.
For example, the ssl23_read() function reports a handshake
failure as follows: SSLerr(SSL_F_SSL23_READ,
SSL_R_SSL_HANDSHAKE_FAILURE);
Function and reason codes should consist of upper case
characters, numbers and underscores only. The error file
generation script translates function codes into function
names by looking in the header files for an appropriate
function name. If none is found it just uses the capitalized
form, such as SSL23_READ in the previous example.
The trailing section of a reason code (after the _R_) is
translated into lower case, and underscores are changed to
spaces.
When you are using new function or reason codes, run the
make errors command. The necessary #defines will automatically
be added to the sublibrary's header file.
Although a library will normally report errors using its
own specific XXXerr() macro, another library's macro can
be used. This is usually done when a library wants to
include ASN1 code which must use the ASN1err() macro.
Adding new libraries [Toc] [Back]
When adding a new sublibrary to OpenSSL, take the following
steps: Assign it a library number, ERR_LIB_XXX.
Define a macro, XXXerr(), (both in <err.h>). Add its name
to ERR_str_libraries[] (in crypto/err/err.c). Add
ERR_load_XXX_strings to the ERR_load _crypto_strings()
function (in crypto/err/err_all.c). Add an entry,
L XXX xxx.h xxx_err.c, to crypto/err/openssl.ec,
and add xxx_err.c to the Makefile.
Running make errors will generate a file,
xxx_err.c, and add all error codes used in the
library to <xxx.h>.
In addition, the library include file must have a certain
form. Typically it will initially look like the following
example:
#ifndef HEADER_XXX_H
#define HEADER_XXX_H
#ifdef __cplusplus
extern "C" {
#endif
/* Include files */
#include <openssl/bio.h>
#include <openssl/x509.h>
/* Macros, structures and function prototypes */
/* BEGIN ERROR CODES */
The BEGIN ERROR CODES sequence is used by the error code
generation script as the point to place new error codes.
Any text after this point will be overwritten when make
errors is run. The closing #endif will be added automatically
by the script.
The generated C error code file xxx_err.c will load the
header files <stdio.h>, <openssl/err.h> and
<openssl/xxx.h> so the header file must load any additional
header files containing any definitions it uses.
Using Error Codes in External Libraries [Toc] [Back]
It also is possible to use OpenSSL's error code scheme in
external libraries. The library needs to load its own
codes and call the OpenSSL error code insertion script
mkerr.pl explicitly to add codes to the header file and
generate the C error code file. This will normally be done
if the external library needs to generate new ASN1 structures
but it can also be used to add more general purpose
error code handling.
Internals [Toc] [Back]
The error queues are stored in a hash table with one
ERR_STATE entry for each pid. The ERR_get_state() function
returns the current thread's ERR_STATE. An ERR_STATE can
hold up to ERR_NUM_ERRORS error codes. When more error
codes are added, the old ones are overwritten, on the
assumption that the most recent errors are most important.
Error strings are also stored in hash tables. The hash
tables can be obtained by calling
ERR_get_err_state_table(void) and
ERR_get_string_table(void), respectively.
Functions: CRYPTO_set_id_callback(3), CRYPTO_set_locking_callback(3), ERR_get_error(3), ERR_GET_LIB(3),
ERR_clear_error(3), ERR_error_string(3),
ERR_print_errors(3), ERR_load_crypto_strings(3),
ERR_remove_state(3), ERR_put_error(3),
ERR_load_strings(3), SSL_get_error(3)
err(3)
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