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DWARF_GET_FDE_INFO_FOR_REG3(3)                        Library Functions Manual

NAME
     dwarf_get_fde_info_for_reg3 -- retrieve register rule

LIBRARY
     DWARF Access Library (libdwarf, -ldwarf)

SYNOPSIS
     #include <libdwarf.h>

     int
     dwarf_get_fde_info_for_reg3(Dwarf_Fde fde, Dwarf_Half table_column,
         Dwarf_Addr pc, Dwarf_Small *type, Dwarf_Signed *offset_relevant,
         Dwarf_Signed *register_num, Dwarf_Signed *offset_or_block_len,
         Dwarf_Ptr *block_ptr, Dwarf_Addr *row_pc, Dwarf_Error *error);

DESCRIPTION
     Function dwarf_get_fde_info_for_reg3() retrieves a register rule from the
     register rule table associated with a given FDE descriptor, given a
     program counter address and rule column number.

     Argument fde should reference a valid DWARF FDE descriptor.

     Arugment table_column should hold the column number of the register rule
     desired.

     Argument pc should hold the program counter address to be used to locate
     the desired register rule row.

     On successful execution, dwarf_get_fde_info_for_reg3() stores information
     about the register rule found into the locations pointed to by the
     arguments type, offset_relevant, register_num, offset_or_block_len,
     block_ptr and row_pc.

     Argument type should point to a location which will hold the type code of
     the register rule found.  The returned value is one of the DW_EXPR_*
     contants defined in the header file <libdwarf.h>.

     If there is an offset value associated with the register rule, the
     location pointed to by argument offset_relevant will be set to 1.

     Argument register_num should point to a location which will hold the
     register number associated with the register rule.

     If the register rule is of type DW_EXPR_OFFSET or DW_EXPR_VAL_OFFSET, the
     location pointed to by argument offset_or_block_len will be set to the
     offset value associated with the register rule, or to 0 if the register
     rule does not have an offset value.  If the type code is
     DW_EXPR_EXPRESSION or DW_EXPR_VAL_EXPRESSION, the location pointed to by
     argument offset_or_block_len will be set to the length in bytes of the
     DWARF expression block associated with the register rule.

     Argument block_ptr should point to a location which will be set to a
     pointer to the content of the DWARF expression block associated with the
     register rule.

     Argument row_pc should point to a location which will be set to the
     lowest program counter address associated with the register rule found.

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

RETURN VALUES
     Function dwarf_get_fde_info_for_reg3() returns DW_DLV_OK when it
     succeeds.  In case of an error, it returns DW_DLV_ERROR and sets the
     argument err.

ERRORS
     Function dwarf_get_fde_info_for_reg3() can fail with:

     [DW_DLE_ARGUMENT]                  One of the arguments block_ptr, fde,
                                        offset_or_block_len, offset_relevant,
                                        register_num, row_pc, or type was
                                        NULL.

     [DW_DLE_FRAME_TABLE_COL_BAD]       The column number provided in argument
                                        table_column was too large.

     [DW_DLE_PC_NOT_IN_FDE_RANGE]       The program counter value provided in
                                        argument pc did not fall in the range
                                        covered by argument fde.

EXAMPLE
     To retrieve the register rules at column 3 from a rule table associated
     with a FDE descriptor:

           Dwarf_Fde fde;
           Dwarf_Off fde_offset, cie_offset;
           Dwarf_Unsigned func_len, fde_length;
           Dwarf_Signed cie_index, offset_relevant, register_num;
           Dwarf_Signed offset_or_block_len;
           Dwarf_Addr low_pc, row_pc;
           Dwarf_Ptr fde_addr, block_ptr;
           Dwarf_Small type;
           Dwarf_Error de;

           /* ... assuming `fde` references a valid FDE descriptor... */
           if (dwarf_get_fde_range(fde, &low_pc, &func_len, &fde_addr,
               &fde_length, &cie_offset, &cie_index, &fde_offset,
               &de) != DW_DLV_OK)
                   errx(EXIT_FAILURE, "dwarf_get_fde_range failed: %s",
                       dwarf_errmsg(de));

           /* Iterate all the table rows. */
           for (pc = low_pc; pc < low_pc + func_len; pc++) {
                   if (dwarf_get_fde_info_for_reg3(fde, 3, pc, &type,
                       &offset_relevant, &register_num, &offset_or_block_len,
                       &block_ptr, &row_pc, &de) != DW_DLV_OK) {
                           warnx("dwarf_get_fde_info_for_reg3 failed: %s",
                               dwarf_errmsg(de));
                           continue;
                   }
                   /* ... use the retrieved register rule ... */
           }

SEE ALSO
     dwarf(3), dwarf_get_fde_at_pc(3), dwarf_get_fde_info_for_all_regs(3),
     dwarf_get_fde_info_for_all_regs3(3), dwarf_get_fde_info_for_cfa_reg3(3),
     dwarf_get_fde_info_for_reg(3), dwarf_get_fde_n(3),
     dwarf_set_frame_cfa_value(3), dwarf_set_frame_rule_table_size(3),
     dwarf_set_frame_rule_initial_value(3), dwarf_set_frame_same_value(3),
     dwarf_set_frame_undefined_value(3)

NetBSD 7.1.2                   November 9, 2011                   NetBSD 7.1.2