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.\" Copyright (c) 2011 Kai Wang
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.\" Id: dwarf_get_vars.3 2071 2011-10-27 03:20:00Z jkoshy
.\"
.Dd April 2, 2011
.Os
.Dt DWARF_GET_VARS 3
.Sh NAME
.Nm dwarf_get_vars ,
.Nm dwarf_var_cu_offset ,
.Nm dwarf_var_die_offset ,
.Nm dwarf_var_name_offsets ,
.Nm dwarf_varname
.Nd retrieve information about static variables
.Sh LIBRARY
.Lb libdwarf
.Sh SYNOPSIS
.In libdwarf.h
.Ft int
.Fo dwarf_get_vars
.Fa "Dwarf_Debug dbg"
.Fa "Dwarf_Var **vars"
.Fa "Dwarf_Signed *nvars"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_var_cu_offset
.Fa "Dwarf_Var var"
.Fa "Dwarf_Off *cu_offset"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_var_die_offset
.Fa "Dwarf_Var var"
.Fa "Dwarf_Off *die_offset"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_var_name_offsets
.Fa "Dwarf_Var var"
.Fa "char **name"
.Fa "Dwarf_Off *die_offset"
.Fa "Dwarf_Off *cu_die_offset"
.Fa "Dwarf_Error *err"
.Fc
.Ft int
.Fo dwarf_varname
.Fa "Dwarf_Var var"
.Fa "char **name"
.Fa "Dwarf_Error *err"
.Fc
.Sh DESCRIPTION
These functions retrieve information about the file scope static
variables associated with a DWARF debug context.
Information about these static variables is returned using opaque
descriptors of type
.Vt Dwarf_Var .
Applications need to use the functions described below to retrieve
the name and offset information contained in these descriptors.
.Pp
Function
.Fn dwarf_get_vars
retrieves descriptors for all the static variables associated with the
DWARF debug context specified by argument
.Ar dbg .
The argument
.Ar vars
should point to a location that will be set to a pointer to an array
of
.Vt Dwarf_Var
descriptors.
The argument
.Ar nvars
should point to a location that will be set to the number of
descriptors returned.
.Pp
Function
.Fn dwarf_var_cu_offset
returns the section-relative offset, relative to the
.Dq ".debug_info"
section, of the compilation unit that
contains the debugging information entry associated with the argument
.Ar var .
Argument
.Ar cu_offset
should point to a location that will hold the returned offset.
.Pp
Function
.Fn dwarf_var_die_offset
retrieves the section-relative offset, relative to the
.Dq ".debug_info"
section, of the debugging information
entry associated with the argument
.Ar var ,
and stores it into the location pointed to by the argument
.Ar die_offset .
.Pp
Function
.Fn dwarf_var_name_offsets
retrieves both the name and the associated offsets for the debugging
information entry for argument
.Ar var .
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 a section-relative
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 a
section-relative offset, relative to the
.Dq ".debug_info"
section, of the first debugging information entry in
the compilation unit associated with argument
.Ar var .
.Pp
Function
.Fn dwarf_varname
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 var .
.Ss Memory Management
The memory area used for the array of
.Vt Dwarf_Var
descriptors returned in argument
.Ar vars
by function
.Fn dwarf_get_vars
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_vars_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_var_name_offsets
and
.Fn dwarf_varname
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 var ,
.Va vars ,
.Va name ,
or
.Va nvars
was NULL.
.El
.Sh SEE ALSO
.Xr dwarf 3 ,
.Xr dwarf_dealloc 3 ,
.Xr dwarf_get_cu_die_offset_given_cu_header_offset 3 ,
.Xr dwarf_vars_dealloc 3