Support Interface Example
The following example creates a support library that prints the section name of any relocatable object file processed as part of a 32-bit link-edit.
$ cat support.c
#include <link.h>
#include <stdio.h>
static int indent = 0;
void
ld_start(const char *name, const Elf32_Half type, const char *caller)
{
(void) printf("output image: %s\n", name);
}
void
ld_file(const char *name, const Elf_Kind kind, int flags, Elf *elf)
{
if (flags & LD_SUP_EXTRACTED)
indent = 4;
else
indent = 2;
(void) printf("%*sfile: %s\n", indent, "", name);
}
void
ld_section(const char *name, Elf32_Shdr *shdr, Elf32_Word sndx,
Elf_Data *data, Elf *elf)
{
Elf32_Ehdr *ehdr = elf32_getehdr(elf);
if (ehdr->e_type == ET_REL)
(void) printf("%*s section [%ld]: %s\n", indent,
"", (long)sndx, name);
}
This support library is dependent upon libelf
to provide the
ELF access function
elf32_getehdr
(3ELF) that is used to determine the input file type. The
support library is built using the following.
$ cc -o support.so.1 -G -K pic support.c -lelf -lc
The following example shows the section diagnostics resulting from the
construction of a trivial application from a relocatable object and a local archive
library. The invocation of the support library, in addition to default debugging
information processing, is brought about by the -S
option
usage.
$ LD_OPTIONS=-S./support.so.1 cc -o prog main.c -L. -lfoo
output image: prog
file: /opt/COMPILER/crti.o
section [1]: .shstrtab
section [2]: .text
....
file: /opt/COMPILER/crt1.o
section [1]: .shstrtab
section [2]: .text
....
file: /opt/COMPILER/values-xt.o
section [1]: .shstrtab
section [2]: .text
....
file: main.o
section [1]: .shstrtab
section [2]: .text
....
file: ./libfoo.a
file: ./libfoo.a(foo.o)
section [1]: .shstrtab
section [2]: .text
....
file: /lib/libc.so
file: /opt/COMPILER/crtn.o
section [1]: .shstrtab
section [2]: .text
....
Note:
The number of sections that are displayed in this example have been reduced to simplify the output. Also, the files included by the compiler driver can vary.