HP-UX Reference (11i v2 07/12) - 3 Library Functions A-M (vol 6)

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elf_begin(3E) elf_begin(3E)
All data associated with an ELF descriptor remain allocated until
elf_end terminates the descriptor’s
last activation. After the descriptors have been terminated, the storage is released; attempting to reference
such data gives undefined behavior. Consequently, a program that deals with multiple input (or output)
files must keep the ELF descriptors active until it finishes with them.
Note
When a program calls
elf_begin on a COFF file, the library translates COFF structures to their ELF
equivalents, allowing programs to read (but not to write) a COFF file as if it were ELF. This conversion
happens only to the memory image and not to the file itself.
EXAMPLES
A prototype for reading a file appears below. If the file is a simple object file, the program executes the loop
one time, receiving a null descriptor in the second iteration. In this case, both
elf and arf will have the
same value, the activation count will be two, and the program calls
elf_end twice to terminate the
descriptor. If the file is an archive, the loop processes each archive member in turn, ignoring those that are
not object files.
if (elf_version(EV_CURRENT) == EV_NONE)
{
/* library out of date */
/* recover from error */
}
cmd = ELF_C_READ;
arf = elf_begin(fildes, cmd, (Elf *)0);
while ((elf = elf_begin(fildes, cmd, arf)) != 0)
{
if ((ehdr = elf32_getehdr(elf)) != 0)
{
/* process the file ...*/
}
cmd = elf_next(elf);
elf_end(elf);
}
elf_end(arf);
Alternatively, the next example illustrates random archive processing. After identifying the file as an
archive, the program repeatedly processes archive members of interest. For clarity, this example omits
error checking and ignores simple object files. Additionally, this fragment preserves the ELF descriptors
for all archive members, because it does not call elf_end to terminate them.
elf_version(EV_CURRENT);
arf = elf_begin(fildes, ELF_C_READ, (Elf *)0);
if (elf_kind(arf) != ELF_K_AR)
{
/* not an archive */
}
/* initial processing */
/* set offset =...fordesired member header */
while (elf_rand(arf, offset) == offset)
{
if ((elf = elf_begin(fildes, ELF_C_READ, arf)) == 0)
break;
if ((ehdr = elf32_getehdr(elf)) != 0)
{
/* process archive member ...*/
}
/* set offset =...fordesired member header */
}
The following outline shows how one might create a new ELF file. This example is simplified to show the
overall flow.
elf_version(EV_CURRENT);
fildes = open("path/name", O_RDWR|O_TRUNC|O_CREAT, 0666);
if ((elf = elf_begin(fildes, ELF_C_WRITE, (Elf *)0)) == 0)
HP-UX 11i Version 2: December 2007 Update − 2 − Hewlett-Packard Company 343