ELFVERSION(3E)                                                ELFVERSION(3E)



NAME
     elfversion - coordinate ELF library and application versions

SYNOPSIS
     cc [flag ...] file ...  -lelf [library ...]

     #include <libelf.h>

     unsigned elfversion(unsigned ver);


DESCRIPTION

     As elf(3E) explains, the program, the library, and an object file have

     independent notions of the ``latest'' ELF version.  elfversion lets a

     program determine the ELF library's internal version.  It further lets

     the program specify what memory types it uses by giving its own working

     version, ver, to the library.  Every program that uses the ELF library

     must coordinate versions as described below.


     The header file <libelf.h> supplies the version to the program with the

     macro EVCURRENT.  If the library's internal version (the highest version

     known to the library) is lower than that known by the program itself, the

     library may lack semantic knowledge assumed by the program.  Accordingly,

     elfversion will not accept a working version unknown to the library.


     Passing ver equal to EVNONE causes elfversion to return the library's

     internal version, without altering the working version.  If ver is a

     version known to the library, elfversion returns the previous (or

     initial) working version number.  Otherwise, the working version remains

     unchanged and elfversion returns EVNONE.


EXAMPLE

     The following excerpt from an application program protects itself from

     using an older library.


          if (elfversion(EVCURRENT) == EVNONE)

          {

                  /* library out of date */

                  /* recover from error */

          }


NOTES

     The working version should be the same for all operations on a particular

     elf descriptor.  Changing the version between operations on a descriptor

     will probably not give the expected results.


SEE ALSO

     elf(3E), elfbegin(3E), elfxlate(3E).









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