NAME
dwarf_loclist,
dwarf_loclist_n —
retrieve DWARF location expression information
LIBRARY
DWARF Access Library (libdwarf, -ldwarf)
SYNOPSIS
#include <libdwarf.h>
int
dwarf_loclist(
Dwarf_Attribute at,
Dwarf_Locdesc **llbuf,
Dwarf_Signed
*listlen,
Dwarf_Error *error);
int
dwarf_loclist_n(
Dwarf_Attribute at,
Dwarf_Locdesc ***llbuf,
Dwarf_Signed
*listlen,
Dwarf_Error *error);
DESCRIPTION
These functions retrieve the location expressions associated with a DWARF
attribute.
Note: function
dwarf_loclist() is deprecated. New application
code should instead use function
dwarf_loclist_n()
Function
dwarf_loclist_n() retrieves the list of location
expressions associated with a DWARF attribute. Argument
at should reference a valid DWARF attribute. Argument
llbuf should point to a location which will hold a
returned array of pointers to
Dwarf_Locdesc descriptors.
Argument
listlen should point to a location which will
be set to the number of elements contained in the returned array. If argument
err is not NULL, it will be used to store error
information in case of an error.
Function
dwarf_loclist() retrieves the first location
expression associated with an attribute. Argument
at
should reference a valid DWARF attribute. Argument
llbuf
should point to a location which will hold the returned pointer to a
Dwarf_Locdesc descriptor. Argument
listlen should point to a location which will be always
set to 1. If argument
err is not NULL, it will be used
to store error information in case of an error.
Dwarf_Locdesc descriptors are defined in the header file
<libdwarf.h>, and consist of
following fields:
- ld_lopc
- The lowest program counter address covered by the
descriptor. This field will be set to 0 if the descriptor is not
associated with an address range.
- ld_hipc
- The highest program counter address covered by the
descriptor. This field will be set to 0 if the descriptor is not
associated with an address range.
- ld_cents
- The number of entries returned in
ld_s field.
- ld_s
- Pointer to an array of Dwarf_Loc
descriptors.
Each
Dwarf_Loc descriptor represents one operation of a
location expression. These descriptors are defined in the header file
<libdwarf.h>, and consist of
following fields:
- lr_atom
- The operator name, one of the
DW_OP_*
constants defined in the header file
<dwarf.h>.
- lr_number
- The first operand of this operation.
- lr_number2
- The second operand of this operation.
- lr_offset
- The byte offset of this operation within the containing
location expression.
Memory Management
The memory area used for the descriptor array returned in argument
llbuf is allocated by the
DWARF Access
Library (libdwarf, -ldwarf). When the descriptor array is no longer
needed, application code should use function
dwarf_dealloc(3) to free
the memory area in the following manner:
- First, the ld_s field of each
Dwarf_Locdesc descriptor should be deallocated using
the allocation type
DW_DLA_LOC_BLOCK
.
- Then, the application should free each
Dwarf_Locdesc descriptor using the allocation type
DW_DLA_LOCDESC
.
- Finally, the llbuf pointer should be
deallocated using the allocation type
DW_DLA_LIST
.
RETURN VALUES
On success, these functions returns
DW_DLV_OK
. In case
of an error, they return
DW_DLV_ERROR
and set the
argument
err.
ERRORS
These functions can fail with:
-
-
- [
DW_DLE_ARGUMENT
]
- One of the arguments at,
llbuf or listlen was
NULL.
-
-
- [
DW_DLE_ARGUMENT
]
- The attribute provided by argument at
does not contain a location expression or is not associated with a
location expression list.
EXAMPLE
To retrieve the location list associated with an attribute, use:
Dwarf_Attribute at;
Dwarf_Locdesc **llbuf;
Dwarf_Signed lcnt;
Dwarf_Loc *lr;
Dwarf_Error de;
int i;
if (dwarf_loclist_n(at, &llbuf, &lcnt, &de) != DW_DLV_OK)
errx(EXIT_FAILURE, "dwarf_loclist_n failed: %s",
dwarf_errmsg(de));
for (i = 0; i < lcnt; i++) {
/* ... Use llbuf[i] ... */
for (j = 0; (Dwarf_Half) j < llbuf[i]->ld_cents; j++) {
lr = &llbuf[i]->ld_s[j];
/* ... Use each Dwarf_Loc descriptor ... */
}
dwarf_dealloc(dbg, llbuf[i]->ld_s, DW_DLA_LOC_BLOCK);
dwarf_dealloc(dbg, llbuf[i], DW_DLA_LOCDESC);
}
dwarf_dealloc(dbg, llbuf, DW_DLA_LIST);
SEE ALSO
dwarf(3),
dwarf_dealloc(3),
dwarf_loclist_from_expr(3),
dwarf_loclist_from_expr_a(3),
dwarf_get_loclist_entry(3)