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Updated: 11 December 1998

OpenVMS Debugger Manual


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C.10.5 Initialization Code

When you debug a program that compiled with the /CHECK=UNDERFLOW or /PARALLEL qualifier, a message appears, as in the following example:


DBG> RUN FORMS
Language: FORTRAN, Module: FORMS 
Type GO to reach main program
DBG>

The "Type GO to reach MAIN program" message indicates that execution is supended before the start of the main program, so that you can execute initialization code under debugger control. Entering the GO command places you at the start of the main program. At that point, enter the GO command again to start program execution, as with other types of Fortran programs.

C.11 MACRO-32

The following subtopics describe debugger support for MACRO-32.

C.11.1 Operators in Language Expressions

The MACRO-32 language does not have expressions in the same sense as high-level languages. Only assembly-time expressions and only a limited set of operators are accepted. To permit the MACRO-32 programmer to use expressions at debug-time as freely as in other languages, the debugger accepts a number of operators in MACRO-32 language expressions that are not found in MACRO-32 itself. In particular, the debugger accepts a complete set of comparison and Boolean operators modeled after BLISS. It also accepts the indirection operator and the normal arithmetic operators.
Kind Symbol Function
Prefix @ Indirection
Prefix . Indirection
Prefix + Unary plus
Prefix - Unary minus (negation)
Infix + Addition
Infix - Subtraction
Infix * Multiplication
Infix / Division
Infix MOD Remainder
Infix @ Left shift
Infix EQL Equal to
Infix EQLU Equal to
Infix NEQ Not equal to
Infix NEQU Not equal to
Infix GTR Greater than
Infix GTRU Greater than unsigned
Infix GEQ Greater than or equal to
Infix GEQU Greater than or equal to unsigned
Infix LSS Less than
Infix LSSU Less than unsigned
Infix LEQ Less than or equal to
Infix LEQU Less than or equal to unsigned
Prefix NOT Bit-wise NOT
Infix AND Bit-wise AND
Infix OR Bit-wise OR
Infix XOR Bit-wise exclusive OR
Infix EQV Bit-wise equivalence

C.11.2 Constructs in Language and Address Expressions

Supported constructs in language and address expressions for MACRO-32 follow:
Symbol Construct
[ ] Subscripting
<p,s,e> Bit field selection as in BLISS

The DST information generated by the MACRO-32 assembler treats a label that is followed by an assembler directive for storage allocation as an array variable whose name is the label. This enables you to use the array syntax of a high-level language when examining or manipulating such data.

In the following example of MACRO-32 source code, the label LAB4 designates hexadecimal data stored in four words:


LAB4:    .WORD    ^X3F,5[2],^X3C 

The debugger treats LAB4 as an array variable. For example, the following command displays the value stored in each element (word):


DBG> EXAMINE LAB4
.MAIN.\MAIN\LAB4 
    [0]:        003F 
    [1]:        0005 
    [2]:        0005 
    [3]:        003C

The following command displays the value stored in the fourth word (the first word is indexed as element "0"):


DBG> EXAMINE LAB4[3]
.MAIN.\MAIN\LAB4[3]:    03C

C.11.3 Data Types

MACRO-32 binds a data type to a label name according to the assembler directive that follows the label definition. Supported MACRO-32 directives follow:
MACRO-32 Directives Operating System Data Type Name
.BYTE Byte Unsigned (BU)
.WORD Word Unsigned (WU)
.LONG Longword Unsigned (LU)
.SIGNED_BYTE Byte Integer (B)
.SIGNED_WORD Word Integer (W)
.LONG Longword Integer (L)
.QUAD Quadword Integer (Q)
.F_FLOATING F_Floating (F)
.D_FLOATING D_Floating (D)
.G_FLOATING G_Floating (G)
.H_FLOATING H_Floating (H) (VAX specific)
(Not applicable) Packed decimal (P)

C.11.4 MACRO-32 Compiler (AMACRO) (Alpha Only)

Programmers who are porting applications written in MACRO-32 to Alpha systems use the MACRO-32 compiler (AMACRO). A debugging session for compiled MACRO-32 code is similar to that for assembled code. However, there are some important differences that are described in this section. For complete information on porting these applications, see the Porting VAX MACRO Code from OpenVMS VAX to OpenVMS Alpha manual.

C.11.4.1 Code Relocation

One major difference is the fact that the code is compiled. On a VAX system, each MACRO-32 instruction is a single machine instruction. On an Alpha system, each MACRO-32 instruction may be compiled into many Alpha machine instructions. A major side effect of this difference is the relocation and rescheduling of code if you do not specify /NOOPTIMIZE in your compile command. After you have debugged your code, you can recompile without /NOOPTIMIZE to improve performance.

C.11.4.2 Symbolic Variables

Another major difference between debugging compiled code and debugging assembled code is a new concept to MACRO--2, the definition of symbolic variables for examining routine arguments. On VAX systems, when you were debugging a routine and wanted to examine the arguments, you would typically do something like the following:


        DBG> EXAMINE @AP        ; to see the argument count 
        DBG> EXAMINE @AP+4      ; to examine the first arg 

or


        DBG> EXAMINE @AP        ; to see arg count 
        DBG> EXAMINE .+4:.+20   ; to see first 5 args 

On Alpha systems, the arguments do not reside in a vector in memory as they did on VAX systems. Furthermore, there is no AP register on Alpha systems. If you type EXAMINE @AP when debugging MACRO compiled code, the debugger reports that AP is an undefined symbol.

In the compiled code, the arguments can reside in some combination of:

The compiler does not require that you read the generated code to locate the arguments. Instead, it provides $ARGn symbols that point to the correct argument locations. $ARG0 is the same as @AP+0 is on VAX systems, that is, the argument count. $ARG1 is the first argument, $ARG2 is the second argument, and so forth. These symbols are defined in CALL_ENTRY and JSB_ENTRY directives, but not in EXCEPTION_ENTRY directives.

C.11.4.3 Locating Arguments Without $ARGn Symbols

There may be additional arguments in your code for which the compiler did not generate a $ARGn symbol. The number of $ARGn symbols defined for a .CALL_ENTRY routine is the maximum number detected by the compiler (either by automatic detection or as specified by MAX_ARGS) or 16, whichever is less. For a .JSB_ENTRY routine, since the arguments are homed in the caller's stack frame and the compiler cannot detect the actual number, it always creates eight $ARGn symbols.

In most cases, you can easily find any additional arguments, but in some cases you cannot.

C.11.4.4 Arguments That Are Easy to Locate

You can easily find additional arguments if:

For example, you can examine arguments beyond the eighth argument in a JSB routine (where the argument list must be homed in the caller), as follows:


  DBG> EX $ARG8  ; highest defined $ARGn
  . 
  . 
  . 
  DBG> EX .+4  ; next arg is in next longword 
  . 
  . 
  . 
  DBG> EX .+4  ; and so on 
 

This example assumes that the caller detected at least ten arguments when homing the argument list.

To find arguments beyond the last $ARGn symbol in a routine that did not home the arguments, proceed exactly as in the previous example except substitute EX .+8 for EX .+4.

C.11.4.5 Arguments That Are Not Easy to Locate

You cannot easily find additional arguments if:

The only way to find the additional arguments in these cases is to examine the compiled machine code to determine where the arguments reside. Both of these problems are eliminated if MAX_ARGS is specified correctly for the maximum argument that you want to examine.

C.11.4.6 Debugging Code with Floating-Point Data

The following list provides important information about debugging compiled MACRO-32 code with floating-point data on an Alpha system:

C.11.4.7 Debugging Code with Packed Decimal Data

The following list provides important information about debugging compiled MACRO-32 code with packed decimal data on an Alpha system:

C.12 MACRO-64 (Alpha Only)

The following subtopics describe debugger support for MACRO-64.

C.12.1 Operators in Language Expressions

Language MACRO-64 does not have expressions in the same sense as high-level languages. Only assembly-time expressions and only a limited set of operators are accepted. To permit the MACRO-64 programmer to use expressions at debug-time as freely as in other languages, the debugger accepts a number of operators in MACRO-64 language expressions that are not found in MACRO-64 itself. In particular, the debugger accepts a complete set of comparison and Boolean operators modeled after BLISS. It also accepts the indirection operator and the normal arithmetic operators.
Kind Symbol Function
Prefix @ Indirection
Prefix . Indirection
Prefix + Unary plus
Prefix - Unary minus (negation)
Infix + Addition
Infix - Subtraction
Infix * Multiplication
Infix / Division
Infix MOD Remainder
Infix @ Left shift
Infix EQL Equal to
Infix EQLU Equal to
Infix NEQ Not equal to
Infix NEQU Not equal to
Infix GTR Greater than
Infix GTRU Greater than unsigned
Infix GEQ Greater than or equal to
Infix GEQU Greater than or equal to unsigned
Infix LSS Less than
Infix LSSU Less than unsigned
Infix LEQ Less than or equal to
Infix LEQU Less than or equal to unsigned
Prefix NOT Bit-wise NOT
Infix AND Bit-wise AND
Infix OR Bit-wise OR
Infix XOR Bit-wise exclusive OR
Infix EQV Bit-wise equivalence

C.12.2 Constructs in Language and Address Expressions

Supported constructs in language and address expressions for MACRO-64 follow:
Symbol Construct
<p,s,e> Bit field selection as in BLISS

C.12.3 Data Types

MACRO-64 binds a data type to a label name according to the data directive that follows the label definition. For example, in the following code fragment, the .LONG data directive directs MACRO-64 to bind the longword integer data type to labels V1, V2, and V3:


.PSECT A, NOEXE 
.BYTE 5 
V1: 
V2: 
V3: .LONG 7 

To confirm the type bound to V1, V2, and V3, issue a SHOW SYMBOL/TYPE command with a V* parameter. The following display results:


   data  .MAIN.\V1 
      atomic type, longword integer, size: 4 bytes 
   data .MAIN.\V2 
      atomic type, longword integer, size: 4 bytes 
   data .MAIN.\V3 
      atomic type, longword integer, size: 4 bytes) 

Supported MACRO-64 directives follow:
MACRO-64 Directives Operating System Data Type Name
.BYTE Byte Unsigned (BU)
.WORD Word Unsigned (WU)
.LONG Longword Unsigned (LU)
.SIGNED_BYTE Byte Integer (B)
.SIGNED_WORD Word Integer (W)
.LONG Longword Integer (L)
.QUAD Quadword Integer (Q)
.F_FLOATING F_Floating (F)
.D_FLOATING D_Floating (D)
.G_FLOATING G_Floating (G)
.S_FLOATING (Alpha specific) S_Floating (S)
.T_FLOATING (Alpha specific) T_Floating (T)
(Not applicable) Packed decimal (P)


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