\"      $NetBSD: dwarf_init.3,v 1.6 2024/03/03 17:37:31 christos Exp $
\"
\" Copyright (c) 2009 Joseph Koshy.  All rights reserved.
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\" Id: dwarf_init.3 3964 2022-03-13 21:41:26Z jkoshy
\"
Dd March 13, 2022
Dt DWARF_INIT 3
Os
Sh NAME
Nm dwarf_init ,
Nm dwarf_elf_init
Nd allocate a DWARF debug descriptor
Sh LIBRARY
Lb libdwarf
Sh SYNOPSIS
In libdwarf.h
Ft int
Fo dwarf_init
Fa "int fd"
Fa "int mode"
Fa "Dwarf_Handler errhand"
Fa "Dwarf_Ptr errarg"
Fa "Dwarf_Debug *ret"
Fa "Dwarf_Error *err"
Fc
Ft int
Fo dwarf_elf_init
Fa "Elf *elf"
Fa "int mode"
Fa "Dwarf_Handler errhand"
Fa "Dwarf_Ptr errarg"
Fa "Dwarf_Debug *ret"
Fa "Dwarf_Error *err"
Fc
Sh DESCRIPTION
These functions allocate and return a
Vt Dwarf_Debug
instance for the object denoted by argument
Fa fd
or
Fa elf .
This instance would be used for subsequent access to debugging information in the object by other functions in the DWARF(3) library.
Pp
For function
Fn dwarf_init ,
argument
Fa fd
denotes an open file descriptor referencing a compilation object.
Function
Fn dwarf_init
implicitly allocates an
Vt Elf
descriptor for argument
Fa fd .
Pp
For function
Fn dwarf_elf_init ,
argument
Fa elf
denotes a descriptor returned by
Xr elf_begin 3
or
Xr elf_memory 3 .
Pp
Argument
Fa mode
specifies the access mode desired.
It should be at least as permissive as the mode with which
the file descriptor
Fa fd
or the ELF descriptor
Fa elf
was created with.
Legal values for argument
Fa mode
are:
Pp
Bl -tag -width "DW_DLC_WRITE" -compact
It DW_DLC_RDWR
Permit reading and writing of DWARF information.
It DW_DLC_READ
Operate in read-only mode.
It DW_DLC_WRITE
Permit writing of DWARF information.
El
Pp
Argument
Fa errhand
denotes a function to be called in case of an error.
If this argument is
Dv NULL
then a default error handling scheme is used.
See
Xr dwarf 3
for a description of the error handling scheme used by the
DWARF(3) library.
Pp
Argument
Fa errarg
is passed to the error handler function denoted by argument
Fa errhand
when it is invoked.
Pp
Argument
Fa ret
points to the memory location that will hold a
Vt Dwarf_Debug
reference on a successful call these functions.
Pp
Argument
Fa err
references a memory location that would hold a
Vt Dwarf_Error
descriptor in case of an error.
Ss Memory Management
The
Vt Dwarf_Debug
instance returned by these functions should be freed using
Fn dwarf_finish .
Sh IMPLEMENTATION NOTES
The current implementation does not support access modes
Dv DW_DLC_RDWR
and
Dv DW_DLC_WRITE .
Sh RETURN VALUES
These functions return the following values:
Bl -tag -width ".Bq Er DW_DLV_NO_ENTRY"
It Bq Er DW_DLV_OK
This return value indicates a successful return.
It Bq Er DW_DLV_ERROR
The operation failed.
It Bq Er DW_DLV_NO_ENTRY
The object specified by arguments
Fa "fd"
or
Fa "elf"
did not contain debug information.
El
Sh EXAMPLES
To initialize a
Vt Dwarf_Debug
instance from a open file descriptor referencing an ELF object, and
with the default error handler, use:
Bd -literal -offset indent
Dwarf_Error err;
Dwarf_Debug dbg;

if (dwarf_init(fd, DW_DLC_READ, NULL, NULL, &dbg, &err) !=
   DW_DLV_OK)
       errx(EXIT_FAILURE, "dwarf_init: %s", dwarf_errmsg(err));
Ed
Sh SEE ALSO
Xr dwarf 3 ,
Xr dwarf_errmsg 3 ,
Xr dwarf_finish 3 ,
Xr dwarf_get_elf 3 ,
Xr elf_begin 3 ,
Xr elf_memory 3

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