ldfcn(FP)

Format

#include <stdio.h>

#include <filehdr.h>
#include <ldfcn.h>

Description

The interface between the calling program and the object file access routines is based on the defined type LDFILE, defined as struct ldfile, declared in the ldfcn.h header file. This structure provides uniform access to both simple object files and object files that are members of an archive file.

The ldopen(S) function allocates and initializes the LDFILE structure and returns a pointer to the structure to the calling program. The members of the LDFILE structure can be accessed individually through macros defined in ldfcn.h and contain the following information:

TYPE(ldptr)

The file magic number used to distinguish between archive members and simple object files

IOPTR(ldptr)

The file pointer returned by fopen and used by the standard input/output functions

OFFSET(ldptr)

The file address of the beginning of the object file; the offset is non-zero if the object file is a member of an archive file.

HEADER(ldptr)

The file header structure of the object file

The object file access functions themselves can be divided into the following categories:

• functions that open or close an object file:

  • ldopen(S) and ldaopen open a common object file

  • ldclose(S) and ldaclose close a common object file

• functions that read header or symbol table information:

  • ldahread(S) reads the archive header of a member of an archive file

  • ldfhread(S) reads the file header of a common object file

  • ldshread(S) and ldnshread read a section header of a common object file

  • ldtbread(S) reads a symbol table entry of a common object file

  • ldgetname(S) retrieves a symbol name from a symbol table entry or from the string table

• functions that position an object file at (seek to) the start of the section, relocation, or line number information for a particular section:

  • ldohseek(S) seeks to the optional file header of a common object file

  • ldsseek(S) and ldnsseek seek to a section of a common object file

  • ldrseek(S) and ldnrseek seek to the relocation information for a section of a common object file

  • ldlseek(S) and ldnlseek seek to the line number information for a section of a common object file

  • ldtbseek(S) seeks to the symbol table of a common object file

• the function ldtbindex(S) which returns the index of a particular common object file symbol table entry.

These functions are described in detail on their respective manual pages. All the functions except ldopen(S), ldgetname(S), and ldtbindex(S) return either SUCCESS or FAILURE, both constants defined in ldfcn.h. ldopen(S) and ldaopen both return pointers to an LDFILE structure.

Additional access to an object file is provided through a set of macros defined in ldfcn.h. They parallel the standard input/output file reading and manipulating functions, translating a reference of the LDFILE structure into a reference to its file descriptor field.

The following macros are provided:

GETC(ldptr)
FGETC(ldptr)
GETW(ldptr)
UNGETC(c, ldptr)
FGETS(s, n, ldptr)
FREAD((char ) ptr, sizeof (ptr), nitems, ldptr)
FSEEK(ldptr, offset, ptrname)
FTELL(ldptr)
REWIND(ldptr)
FEOF(ldptr)
FERROR(ldptr)
FILENO(ldptr)
SETBUF(ldptr, buf)
STROFFSET(ldptr)

The STROFFSET macro calculates the address of the string table. See the manual entries for the corresponding standard input/output library functions for details on the use of the rest of the macros.

The program must be loaded with the object file access library routine LIBDIR/elibld.a.

Warning

See also

Standards conformance