elf_version(3E)                (ELF Library)                elf_version(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                      /* library out of date */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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