DWARF_NEW_EXPR(3)

NAME
dwarf_new_expr - create a location expression descriptor

LIBRARY
libdwarf

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.

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;
    }

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.

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