DWARF_OBJECT_INIT(3) |
Library Functions Manual |
DWARF_OBJECT_INIT(3) |
NAME
dwarf_object_init — allocate a DWARF debug descriptor with application-specific file access methods
LIBRARY
DWARF Access Library (libdwarf, -ldwarf)
SYNOPSIS
#include <libdwarf.h>
int
dwarf_object_init(Dwarf_Obj_Access_Interface *iface, Dwarf_Handler errhand, Dwarf_Ptr errarg, Dwarf_Debug *dbg, Dwarf_Error *err);
DESCRIPTION
The
dwarf_object_init() function allocates and returns a
Dwarf_Debug instance that uses application-supplied access methods to read file content.
The argument iface should point to a populated Dwarf_Obj_Access_Interface structure. The contents of the Dwarf_Obj_Access_Interface structure are described in the section Object Access Functions below.
The argument errhand should point to a function to be called in case of an error. If this argument is NULL then a default error handling scheme is used. See dwarf(3) for a description of the error handling schemes available.
The argument errarg will be passed to the error handler function pointed to by argument errhand.
The argument dbg should point to a memory location that will be set to a reference to the returned Dwarf_Debug descriptor.
The argument err will be used to return a Dwarf_Error descriptor in case of an error.
Object Access Functions
The data structures used to specify object access methods are defined in
<libdwarf.h>.
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Dwarf_Obj_Access_Interface
-
This structure bundles together a set of file access methods along with a pointer to application-private state.
typedef struct {
void *object;
const Dwarf_Obj_Access_Methods *methods;
} Dwarf_Obj_Access_Interface;
-
object
-
This field points to application-specific state that will be passed as the first parameter to the actual access object methods.
-
methods
-
This structure contains pointers to the functions implementing the access methods, as described below.
-
Dwarf_Obj_Access_Methods
-
This structure specifies the functions implementing low-level access.
typedef struct {
int (*get_section_info)(void *obj, Dwarf_Half index,
Dwarf_Obj_Access_Section *ret, int *error);
Dwarf_Endianness (*get_byte_order)(void *obj);
Dwarf_Small (*get_length_size)(void *obj);
Dwarf_Small (*get_pointer_size)(void *obj);
Dwarf_Unsigned (*get_section_count)(void *obj);
int (*load_section)(void *obj, Dwarf_Half ndx,
Dwarf_Small **ret_data, int *error);
} Dwarf_Obj_Access_Methods;
-
get_byte_order
-
This function should return the endianness of the DWARF object by returning one of the constants DW_OBJECT_MSB or DW_OBJECT_LSB.
-
get_length_size
-
This function should return the number of bytes needed to represent a DWARF offset in the object being debugged.
-
get_pointer_size
-
This function should return the size in bytes, in the object being debugged, of a memory address.
-
get_section_count
-
This function should return the number of sections in the object being debugged.
-
get_section_info
-
This function should return information about the section at the index ndx by filling in the structure of type Dwarf_Obj_Access_Section pointed to by argument ret. The Dwarf_Obj_Access_Section structure is described below.
-
load_section
-
This function should load the section specified by argument ndx into memory and place a pointer to the section's data into the location pointed to by argument ret_data.
The argument obj passed to these functions will be set to the pointer value in the object field of the associated Dwarf_Obj_Access_Interface structure.
The argument error is used to return an error code in case of an error.
-
Dwarf_Obj_Access_Section
-
This structure describes the layout of a section in the DWARF object.
typedef struct {
Dwarf_Addr addr;
Dwarf_Unsigned size;
const char *name;
} Dwarf_Obj_Access_Section;
-
addr
-
A pointer to the start of the section's data.
-
size
-
The size of the section in bytes.
-
name
-
A pointer to a NUL-terminated string containing the name of the section.
RETURN VALUES
On success, the dwarf_object_init() function returns DW_DLV_OK. In case of an error, the function returns DW_DLV_ERROR and sets the argument err.
ERRORS
The
dwarf_object_init() function may fail with the following errors:
-
[DW_DLE_ARGUMENT]
-
One of the arguments iface or dbg was NULL.
-
[DW_DLE_DEBUG_INFO_NULL]
-
The underlying object did not contain debugging information.
-
[DW_DLE_MEMORY]
-
An out of memory condition was encountered during the execution of the function.