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DWARF_LOCLIST(3)           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 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:

     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)

NetBSD 10.99                   November 9, 2011                   NetBSD 10.99