NAME

dwarf_attrval_flag, dwarf_attrval_signed, dwarf_attrval_string, dwarf_attrval_unsigned —

retrieve the value of an attribute within a DWARF debugging information entry

LIBRARY

DWARF Access Library (libdwarf, -ldwarf)

SYNOPSIS

#include <libdwarf.h>

int
dwarf_attrval_flag(Dwarf_Die die, Dwarf_Half attr, Dwarf_Bool *ret, Dwarf_Error *err);

int
dwarf_attrval_signed(Dwarf_Die die, Dwarf_Half attr, Dwarf_Signed *ret, Dwarf_Error *err);

int
dwarf_attrval_string(Dwarf_Die die, Dwarf_Half attr, const char **ret, Dwarf_Error *err);

int
dwarf_attrval_unsigned(Dwarf_Die die, Dwarf_Half attr, Dwarf_Unsigned *ret, Dwarf_Error *err);

DESCRIPTION

These functions search the debugging information entry referenced by argument die for the attribute named by argument attr. If the named attribute is found, the functions set the location pointed to by argument ret to the value of the attribute. The argument err, if non NULL, will be used to return an error descriptor in case of an error.

Function dwarf_attrval_flag() sets the location pointed to by argument ret to either 0 or 1. If the form of the attribute named by argument attr is DW_FORM_flag, function dwarf_attrval_flag() sets the location pointed to by argument ret to 1 if the attribute has a non-zero value, or to 0 otherwise. If the form of the attribute named by argument attr is DW_FORM_flag_present, function dwarf_attrval_flag() unconditionally sets the location pointed to by argument ret to 1. The form of the attribute must be one of DW_FORM_flag or DW_FORM_flag_present.

Function dwarf_attrval_signed() stores the value for the attribute named by argument attr, into the location pointed to by argument ret. The attribute's value is treated as a signed integral quantity and is sign-extended as needed. The attribute named by the argument attr must belong to the CONSTANT class and must have one of the following forms: DW_FORM_data1, DW_FORM_data2, DW_FORM_data4, DW_FORM_data8 or DW_FORM_sdata.

Function dwarf_attrval_string() sets the location pointed to by argument ret to a pointer to a NUL-terminated string that is the value of the attribute named by argument attr. The form of the attribute must be one of DW_FORM_string or DW_FORM_strp.

Function dwarf_attrval_unsigned() stores the value for the attribute named by argument attr into the location pointed to by argument ret. The attribute's value is treated as an unsigned integral quantity, and is zero-extended as needed. The named attribute must belong to one of the CONSTANT, ADDRESS or REFERENCE classes and must have one of the following forms: DW_FORM_addr, DW_FORM_data1, DW_FORM_data2, DW_FORM_data4, DW_FORM_data8, DW_FORM_udata, DW_FORM_ref1, DW_FORM_ref2, DW_FORM_ref4, DW_FORM_ref8, or DW_FORM_ref_udata.

If the attribute named by argument attr is DW_AT_type and is not present in the debugging information entry referenced by argument die, and if a DW_AT_abstract_origin or DW_AT_specification attribute is present in the debugging information entry, function dwarf_attrval_unsigned() will search for the named attribute in the debugging information entry referenced by the DW_AT_abstract_origin or DW_AT_specification attribute.

RETURN VALUES

On success, these functions returns DW_DLV_OK. If the named attribute was not found in the specified debugging information entry descriptor these functions return DW_DLV_NO_ENTRY and set argument err. For other errors, these functions return DW_DLV_ERROR and set argument err.

COMPATIBILITY

These functions are extensions added by this implementation of the DWARF(3) API.

ERRORS

These functions may fail with the following errors:

[DW_DLE_ARGUMENT]: Either of the arguments die or ret was NULL.
[DW_DLE_NO_ENTRY]: Argument die did not contain an attribute corresponding to the value in argument attr.
[DW_DLE_ATTR_FORM_BAD]: The attribute named by argument attr was not of a permitted form.