dwarf_loclist,
dwarf_loclist_n —
retrieve DWARF location expression
information
DWARF Access Library (libdwarf, -ldwarf)
#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);
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.
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
.
On success, these functions returns
DW_DLV_OK
. In case of an error, they return
DW_DLV_ERROR
and set the argument
err.
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);
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.
dwarf(3),
dwarf_dealloc(3),
dwarf_get_loclist_entry(3),
dwarf_loclist_from_expr(3),
dwarf_loclist_from_expr_a(3)