.\" Copyright (c) 2011 Kai Wang
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.\" $Id: dwarf_get_weaks.3 2071 2011-10-27 03:20:00Z jkoshy $
.\"
.Dd April 10, 2011
.Os
.Dt DWARF_GET_WEAKS 3
.Sh NAME
.Nm dwarf_get_weaks ,
.Nm dwarf_weak_cu_offset ,
.Nm dwarf_weak_die_offset ,
.Nm dwarf_weak_name_offsets ,
.Nm dwarf_weakname
.Nd retrieve information about weak symbols
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft int
.Fo dwarf_get_weaks
.Fa "Dwarf_Debug dbg"
.Fa "Dwarf_Weak **weaks"
.Fa "Dwarf_Signed *nweaks"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_weak_cu_offset
.Fa "Dwarf_Weak weak"
.Fa "Dwarf_Off *cu_offset"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_weak_die_offset
.Fa "Dwarf_Weak weak"
.Fa "Dwarf_Off *die_offset"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_weak_name_offsets
.Fa "Dwarf_Weak weak"
.Fa "char **name"
.Fa "Dwarf_Off *die_offset"
.Fa "Dwarf_Off *cu_die_offset"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_weakname
.Fa "Dwarf_Weak weak"
.Fa "char **name"
.Fa "Dwarf_Error *err"
.Fc
.Sh DESCRIPTION
These functions retrieve information about weak symbols from the
lookup tables in the (SGI-specific)
.Dq ".debug_weaknames"
section.
Information about weak symbols is returned using opaque descriptors
of type
.Vt Dwarf_Weak .
Applications need to use the functions described below to retrieve
the name and offset information contained in these descriptors.
.Pp
Function
.Fn dwarf_get_weaks
retrieves descriptors for all the weak symbols associated with the
DWARF debug context specified by argument
.Ar dbg .
The argument
.Ar weaks
should point to a location that will be set to a pointer to an array
of
.Vt Dwarf_Weak
descriptors.
The argument
.Ar nweaks
should point to a location that will be set to the number of
descriptors returned.
.Pp
Function
.Fn dwarf_weak_cu_offset
returns the offset, relative to the
.Dq ".debug_info"
section, of the compilation unit that contains the debugging
information entry associated with the argument
.Ar weak .
Argument
.Ar cu_offset
should point to a location that will hold the returned offset.
.Pp
Function
.Fn dwarf_weak_die_offset
retrieves the offset, relative to the
.Dq ".debug_info"
section, of the debugging information entry associated with the
argument
.Ar weak ,
and stores it into the location pointed to by the argument
.Ar die_offset .
.Pp
Function
.Fn dwarf_weak_name_offsets
retrieves the name and offsets for the debugging information
entry for argument
.Ar weak .
Argument
.Ar name
should point to a location which will be set to a pointer to a
NUL-terminated string containing the name of the associated debugging
information entry.
Argument
.Ar die_offset
should point to a location which will be set to the offset, relative
to the
.Dq ".debug_info"
section, of the associated debugging information entry.
Argument
.Ar cu_die_offset
should point to a location which will be set to the
offset, relative to the
.Dq ".debug_info"
section, of the first debugging information entry in the compilation
unit associated with argument
.Ar weak .
.Pp
Function
.Fn dwarf_weakname
sets the location pointed to by argument
.Ar name
to a pointer to a NUL-terminated string holding the name of the
debugging information entry associated with the argument
.Ar weak .
.Ss Memory Management
The memory area used for the array of
.Vt Dwarf_Weak
descriptors returned in argument
.Ar weaks
by function
.Fn dwarf_get_weaks
is owned by the
.Lb libdwarf .
Application code should not attempt to directly free this pointer.
Portable code should instead use the function
.Xr dwarf_weaks_dealloc 3
to indicate that the memory area may be freed.
.Pp
The memory area used for the string returned in the
.Ar name
argument to functions
.Fn dwarf_weak_name_offsets
and
.Fn dwarf_weakname
is owned by the
.Lb libdwarf .
Portable code should indicate that the memory area can
be freed using the
.Xr dwarf_dealloc 3
function.
.Ss Error Returns
If argument
.Ar err
is not NULL, these functions will use it to store error information,
in case of an error.
.Sh RETURN VALUES
On success, these functions returns
.Dv DW_DLV_OK .
In case of an error, they return
.Dv DW_DLV_ERROR
and set the argument
.Ar err .
.Sh ERRORS
These functions may fail with the following errors:
.Bl -tag -width ".Bq Er DW_DLE_ARGUMENT"
.It Bq Er DW_DLE_ARGUMENT
One of the arguments
.Va cu_die_offset ,
.Va cu_offset ,
.Va dbg ,
.Va die_offset ,
.Va weak ,
.Va weaks ,
.Va name ,
or
.Va nweaks
was NULL.
.It Bq Er DW_DLE_NO_ENTRY
The DWARF debugging context referenced by argument
.Ar dbg
did not contain information about weak symbols.
.El
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_get_cu_die_offset_given_cu_header_offset 3 ,
.Xr dwarf_weaks_dealloc 3