dwarf_new_expr —
create a location expression descriptor
DWARF Access Library (libdwarf, -ldwarf)
#include
<libdwarf.h>
Dwarf_P_Expr
dwarf_new_expr(
Dwarf_P_Debug
dbg,
Dwarf_Error *err);
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.
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.
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;
}
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.
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)