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DWARF_NEW_EXPR(3)          Library Functions Manual          DWARF_NEW_EXPR(3)

NAME
     dwarf_new_expr -- create a location expression descriptor

LIBRARY
     DWARF Access Library (libdwarf, -ldwarf)

SYNOPSIS
     #include <libdwarf.h>

     Dwarf_P_Expr
     dwarf_new_expr(Dwarf_P_Debug dbg, Dwarf_Error *err);

DESCRIPTION
     Function dwarf_new_expr() allocates a DWARF location expression
     descriptor used to build up a location expression stream.

     The application can use the functions dwarf_add_expr_gen(3) and
     dwarf_add_expr_addr_b(3) to add location expression operators to the
     created descriptor.  When done, the application can call the function
     dwarf_expr_into_block(3) to retrieve the generated byte stream for the
     location expression, or call the function dwarf_add_AT_location_expr(3)
     to create an attribute with the location expression stream as its value.

     Argument dbg should reference a DWARF producer instance allocated using
     dwarf_producer_init(3) or dwarf_producer_init_b(3).

     If argument err is not NULL, it will be used to store error information
     in case of an error.

RETURN VALUES
     On success, function dwarf_new_expr() returns the created location
     expression descriptor.  In case of an error, function dwarf_new_expr()
     returns DW_DLV_BADADDR and sets the argument err.

ERRORS
     Function dwarf_new_expr() can fail with:

     [DW_DLE_ARGUMENT]       Argument dbg was NULL.

     [DW_DLE_MEMORY]         An out of memory condition was encountered during
                             the execution of the function.

EXAMPLES
     To create a location expression descriptor, add location expression
     operators to it and to retrieve the generated byte stream, use:

           Dwarf_P_Debug dbg;
           Dwarf_Error de;
           Dwarf_P_Expr pe;
           Dwarf_Addr buf;
           Dwarf_Unsigned len;

           /* ...Assume that `dbg' refers to a DWARF producer instance... */

           if ((pe = dwarf_new_expr(dbg, &de)) == DW_DLV_BADADDR) {
                   warnx("dwarf_new_expr failed: %s", dwarf_errmsg(-1));
                   return;
           }

           if (dwarf_add_expr_gen(pe, DW_OP_regx, 55, 0, &de) ==
               DW_DLV_NOCOUNT) {
                   warnx("dwarf_add_expr_gen failed: %s", dwarf_errmsg(-1));
                   return;
           }

           if ((buf = dwarf_expr_into_block(pe, &len, &de)) ==
               DW_DLV_BADADDR) {
                   warnx("dwarf_expr_into_block failed: %s",
                       dwarf_errmsg(-1));
                   return;
           }

SEE ALSO
     dwarf(3), dwarf_add_AT_location_expr(3), dwarf_add_expr_gen(3),
     dwarf_add_expr_addr(3), dwarf_add_expr_addr_b(3),
     dwarf_expr_current_offset(3), dwarf_expr_into_block(3),
     dwarf_producer_init(3), dwarf_producer_init_b(3)

NetBSD 7.1.2                   September 8, 2011                  NetBSD 7.1.2