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err(3)									err(3)

NAME
       err - Error codes

SYNOPSIS
       #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 );

DESCRIPTION
       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 associ‐
       ated  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 mes‐
       sages 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.

ERRORS
       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
       Each  sublibrary has a specific macro, XXXerr(), that is used to report
       errors. Its first argument is a function code, XXX_F_..., and the  sec‐
       ond  argument  is  a reason code, XXX_R_.... Function codes are derived
       from the function names; reason codes consist of textual error descrip‐
       tions. For example, the ssl23_read() function reports a handshake fail‐
       ure as follows: SSLerr(SSL_F_SSL23_READ, SSL_R_SSL_HANDSHAKE_FAILURE);

       Function and reason codes should consist of upper case characters, num‐
       bers  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 capi‐
       talized 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 sub‐
       library'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
       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. Typi‐
       cally 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
       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  han‐
       dling.

   Internals
       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.

SEE ALSO
       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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