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$Id: dwarf_object_init.3 3644 2018-10-15 19:55:01Z jkoshy $
.Dd September 29, 2011 .Dt DWARF_OBJECT_INIT 3 .Os .Sh NAME .Nm dwarf_object_init .Nd allocate a DWARF debug descriptor with application-specific file \ access methods .Sh LIBRARY .Lb libdwarf .Sh SYNOPSIS n libdwarf.h .Ft int .Fo dwarf_object_init .Fa "Dwarf_Obj_Access_Interface *iface" .Fa "Dwarf_Handler errhand" .Fa "Dwarf_Ptr errarg" .Fa "Dwarf_Debug *dbg" .Fa "Dwarf_Error *err" .Fc .Sh DESCRIPTION The .Fn dwarf_object_init function allocates and returns a .Vt Dwarf_Debug instance that uses application-supplied access methods to read file content.
p The argument .Ar iface should point to a populated .Vt Dwarf_Obj_Access_Interface structure. The contents of the .Vt Dwarf_Obj_Access_Interface structure are described in the section .Sx "Object Access Functions" below.
p The argument .Ar errhand should point to a function to be called in case of an error. If this argument is .Dv NULL then a default error handling scheme is used. See .Xr dwarf 3 for a description of the error handling schemes available.
p The argument .Ar errarg will be passed to the error handler function pointed to by argument .Ar errhand .
p The argument .Ar dbg should point to a memory location that will be set to a reference to the returned .Vt Dwarf_Debug descriptor.
p The argument .Ar err will be used to return a .Vt Dwarf_Error descriptor in case of an error. .Ss Object Access Functions The data structures used to specify object access methods are defined in n libdwarf.h . l -tag -width indent t Vt "Dwarf_Obj_Access_Interface" This structure bundles together a set of file access methods along with a pointer to application-private state. d -literal -offset indent typedef struct { void *object; const Dwarf_Obj_Access_Methods *methods; } Dwarf_Obj_Access_Interface; .Ed
p l -tag -width ".Ar methods" -compact t Ar object This field points to application-specific state that will be passed as the first parameter to the actual access object methods. t Ar methods This structure contains pointers to the functions implementing the access methods, as described below. .El t Vt Dwarf_Obj_Access_Methods This structure specifies the functions implementing low-level access. d -literal -offset indent 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; .Ed
p l -tag -width ".Ar get_section_count" -compact t Ar get_byte_order This function should return the endianness of the DWARF object by returning one of the constants .Dv DW_OBJECT_MSB or .Dv DW_OBJECT_LSB . t Ar get_length_size This function should return the number of bytes needed to represent a DWARF offset in the object being debugged. t Ar get_pointer_size This function should return the size in bytes, in the object being debugged, of a memory address. t Ar get_section_count This function should return the number of sections in the object being debugged. t Ar get_section_info This function should return information about the section at the index .Ar ndx by filling in the structure of type .Vt Dwarf_Obj_Access_Section pointed to by argument .Ar ret . The .Vt Dwarf_Obj_Access_Section structure is described below. t Ar load_section This function should load the section specified by argument .Ar ndx into memory and place a pointer to the section's data into the location pointed to by argument .Ar ret_data . .El
p The argument .Ar obj passed to these functions will be set to the pointer value in the .Ar object field of the associated .Vt Dwarf_Obj_Access_Interface structure.
p The argument .Ar error is used to return an error code in case of an error. t Vt Dwarf_Obj_Access_Section This structure describes the layout of a section in the DWARF object. d -literal -offset indent typedef struct { Dwarf_Addr addr; Dwarf_Unsigned size; const char *name; } Dwarf_Obj_Access_Section; .Ed
p l -tag -width ".Ar name" -compact t Ar addr A pointer to the start of the section's data. t Ar size The size of the section in bytes. t Ar name A pointer to a NUL-terminated string containing the name of the section. .El .El .Sh RETURN VALUES On success, the .Fn dwarf_object_init function returns .Dv DW_DLV_OK . In case of an error, the function returns .Dv DW_DLV_ERROR and sets the argument .Ar err . .Sh ERRORS The .Fn dwarf_object_init function may fail with the following errors: l -tag -width ".Bq Er DW_DLE_DEBUG_INFO_NULL" t Bq Er DW_DLE_ARGUMENT One of the arguments .Ar iface or .Ar dbg was NULL. t Bq Er DW_DLE_DEBUG_INFO_NULL The underlying object did not contain debugging information. t Bq Er DW_DLE_MEMORY An out of memory condition was encountered during the execution of the function. .El .Sh SEE ALSO .Xr dwarf 3 , .Xr dwarf_init 3 , .Xr dwarf_init_elf 3 , .Xr dwarf_object_finish 3