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DWARF_LOCLIST(3) FreeBSD Library Functions Manual DWARF_LOCLIST(3)
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 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:
1. First, the ld_s field of each Dwarf_Locdesc descriptor should be
deallocated using the allocation type DW_DLA_LOC_BLOCK.
2. Then, the application should free each Dwarf_Locdesc descriptor
using the allocation type DW_DLA_LOCDESC.
3. 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.
EXAMPLES
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);
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.
SEE ALSO
dwarf(3), dwarf_dealloc(3), dwarf_get_loclist_entry(3),
dwarf_loclist_from_expr(3), dwarf_loclist_from_expr_a(3)
FreeBSD 14.0-RELEASE-p11 November 9, 2011 FreeBSD 14.0-RELEASE-p11