Assembler Language Reference

.tbtag Pseudo-op

Purpose

Defines a debug traceback tag, preceded by a word of zeros, that can perform tracebacks for debugging programs.

Syntax

.tbtag Expression1, Expression2, Expression3, Expression4, Expression5, Expression6, Expression7, Expression8,[ Expression9, Expression10, Expression11, Expression12, Expression13, Expression14, Expression15, Expression16]

Description

The .tbtag pseudo-op defines a traceback tag by assembling Expressions into consecutive bytes, words, and halfwords, depending on field requirements. An instruction can contain either 8 expressions (Expression1 through Expression8) or 16 expressions (Expression1 through Expression16). Anything else is a syntax error. A compiler customarily inserts the traceback information into a program at the end of the machine instructions, adding a string of zeros to signal the start of the information.

Parameters

Expression1	version	/Traceback format version /
Byte
Expression2	lang	/Language values /
Byte
	TB_C	0
	TB_FORTRAN	1
	TB_PASCAL	2
	TB_ADA	3
	TB_PL1	4
	TB_BASIC	5
	TB_LISP	6
	TB_COBOL	7
	TB_MODULA2	8
	TB_CPLUSPLUS	9
	TB_RPG	10
	TB_PL8	11
	TB_ASM	12
Expression3		/Traceback control bits /
Byte
	globallink	Bit 7. Set if routine is global linkage.
	is_eprol	Bit 6. Set if out-of-town epilog/prologue.
	has_tboff	Bit 5. Set if offset from start of proc stored.
	int_proc	Bit 4. Set if routine is internal.
	has_ctl	Bit 3. Set if routine involves controlled storage.
	tocless	Bit 2. Set if routine contains no TOC.
	fp_present	Bit 1. Set if routine performs FP operations.
	log_abort	Bit 0. Set if routine involves controlled storage.
Expression4		/Traceback control bits (continued) /
Byte
	int_hndl	Bit 7. Set if routine is interrupt handler.
	name_present	Bit 6. Set if name is present in proc table.
	uses_alloca	Bit 5. Set if alloca used to allocate storage.
	cl_dis_inv	Bits 4, 3, 2. On-condition directives
		WALK_ONCOND	0	Walk stack; don't restore state
		DISCARD_ONCOND	1	Walk the stack and discard.
		INVOKE_ONCOND	1	Invoke specific system routine
	saves_cr	Bit 1. Set if procedure saves condition register.
	saves_lr	Bit 0. Set if procedure saves link register.
Expression5		/Traceback control bits (continued) /
Byte
	stores_bc	Bit 7. Set if procedure stores the backchain.
	spare2	Bit 6. Spare bit.
	fpr_saved	Bits 5, 4, 3, 2, 1, 0. Number of FPRs saved, max 32.
Expression6		/Traceback control bits (continued) /
Byte
	spare3	Bits 7, 6. Spare bits.
	gpr_saved	Bits 5, 4, 3, 2, 1, 0. Number of GPRs saved, max 32.
Expression7	fixedparms	/Traceback control bits (continued) /
Byte
Expression8
Byte
	floatparms	Bits 7, 6, 5, 4, 3, 2,1. Number of floating point parameters.
	parmsonstk	Bit 0. Set if all parameters placed on stack.
Expression9	parminfo	/Order and type coding of parameters /
Word
	'0'	Fixed parameter.
	'10'	Single-precision float parameter.
	'11'	Double-precision float parameter.
Expression10	tb_offset	/Offset from start of code to tb table /
Word
Expression11	hand_mask	/What interrupts are handled /
Word
Expression12	ctl_info	/Number of CTL anchors /
Word
Expression13	ctl_info_disp	/Displacements of each anchor into stack/
Word
Expression14	name_len	/Length of procedure name /
Halfword
Expression15	name	/Name /
Byte
Expression16	alloca_reg	/Register for alloca automatic storage/
Byte

Examples

The following example illustrates the use of the .tbtag pseudo-op:

   .tbtag 1,0,0xff,0,0,16,0,0

Related Information

Pseudo-ops Overview.

Traceback Tags.

.byte Pseudo-op.