Common Object File Format (COFF)

Type entry

The type field in the symbol table entry contains information about the basic and derived type for the symbol. This information is generated by the C compilation system only if the -g option is used. Each symbol has exactly one basic or fundamental type but can have more than one derived type. The format of the 16-bit type entry is:

d6 d5 d4 d3 d2 d1 typ

Bits 0 through 3, called typ, indicate one of the fundamental types given in ``Fundamental types''.

Fundamental types

Mnemonic Value Type

T_NULL 0 type not assigned T_ARG

1 function argument

(used only by compiler) T_CHAR

2 character T_SHORT

3 short integer T_INT

4 integer T_LONG

5 long integer T_FLOAT

6 floating point T_DOUBLE

7 double word T_STRUCT

8 structure T_UNION

9 union T_ENUM

10 enumeration T_MOE

11 member of enumeration T_UCHAR

12 unsigned character T_USHORT

13 unsigned short T_UINT

14 unsigned integer T_ULONG

15 unsigned long

Mnemonic	Value	Type
T_NULL	0	type not assigned	T_ARG
1	function argument
	(used only by compiler)		T_CHAR
2	character		T_SHORT
3	short integer		T_INT
4	integer		T_LONG
5	long integer		T_FLOAT
6	floating point		T_DOUBLE
7	double word		T_STRUCT
8	structure		T_UNION
9	union		T_ENUM
10	enumeration		T_MOE
11	member of enumeration		T_UCHAR
12	unsigned character		T_USHORT
13	unsigned short		T_UINT
14	unsigned integer		T_ULONG
15	unsigned long

Bits 4 through 15 are arranged as six 2-bit fields marked d1 through d6. These d fields represent levels of the derived types given in ``Derived types''.

Derived types

Mnemonic Value Type

DT_NON 0 no derived type

DT_PTR 1 pointer

DT_FCN 2 function

DT_ARY 3 array

Mnemonic	Value	Type
DT_NON	0	no derived type
DT_PTR	1	pointer
DT_FCN	2	function
DT_ARY	3	array

The following examples demonstrate the interpretation of the symbol table entry representing type:

   char *func();

Here func is the name of a function that returns a pointer to a character. The fundamental type of func is 2 (character), the d1 field is 2 (function), and the d2 field is 1 (pointer). Therefore, the type word in the symbol table for func contains the hexadecimal number 0x62, which is interpreted to mean a function that returns a pointer to a character:

   short *tabptr[10][25][3];

Here tabptr is a three-dimensional array of pointers to short integers. The fundamental type of tabptr is 3 (short integer); the d1, d2, and d3 fields each contains a 3 (array), and the d4 field is 1 (pointer). Therefore, the type entry in the symbol table contains the hexadecimal number 0x7f3 indicating a three-dimensional array of pointers to short integers.