Assembler diagnostics

This page lists every diagnostic currently emitted by the MB8 assembler. The diagnostic code in the command-line output links directly to the corresponding section below.

A0100

Lex Error

The assembler found a character, malformed hexadecimal number, string escape, or unterminated string that cannot be converted into a token.

Example

LDI R1, 42

Decimal literals are not part of the assembly syntax.

How to fix

Use a hexadecimal literal and make sure strings contain only supported escapes.

LDI R1, 0x2A

A0101

Parse Error

The tokens are valid individually, but they do not form a valid instruction, label, or directive. This commonly means that punctuation or an operand is missing.

Example

LDI R1 0x2A

How to fix

Follow the required instruction form, including the comma between operands.

LDI R1, 0x2A

A0200

Include Error

The assembler could not read or expand a file named by an .include directive. The diagnostic message contains the underlying file or include error.

Example

.include "missing.asm"

How to fix

Correct the path, create the included file, or fix its permissions. Include paths are resolved relative to the file containing the directive.

A0300

Unsupported Instruction Form

The mnemonic and operands do not match any core instruction or pseudo-instruction known to the assembler.

Example

MOV R1, 0x01

How to fix

Use a supported operand form. For example, load an immediate value with LDI.

LDI R1, 0x01

A0301

Duplicate Label

The same label is defined more than once in its scope. The diagnostic marks both definitions.

Example

loop:
    NOP
loop:
    HALT

How to fix

Rename or remove one definition, and update any references to the renamed label.

loop:
    NOP
done:
    HALT

A0302

Unknown Label

An instruction refers to a label that is not defined in the applicable source scope.

Example

JMP missing

How to fix

Define the label or correct its spelling.

JMP done

done:
    HALT

A0303

Unexpected Directive After Include Expansion

An .include or .const directive reached an internal assembler stage where it should already have been expanded or removed. This indicates an assembler bug, not an error that assembly source is normally expected to cause.

How to fix

Please report the bug and include the source files, assembler version, and full diagnostic output.

A0304

Duplicate Origin Directive

An assembled program contains more than one .origin directive. The diagnostic marks the first and duplicate directives.

Example

.origin 0x1000
.origin 0x2000

How to fix

Keep a single .origin directive in the root source.

.origin 0x1000

A0305

Address Overflow

Emitting an instruction or data would advance the current address beyond 0xFFFF, the largest address representable by the assembler.

Example

.origin 0xFFFF
NOP

How to fix

Move the origin to a lower address or reduce the amount of emitted code or data.

.origin 0xFFFD
NOP

A0306

Value Out of Range

An immediate value does not fit the operand width required by the selected instruction form.

Example

LDI R1, 0x0100

How to fix

Use a value within the stated range or an instruction form that accepts the wider value.

LDI R1, 0xFF

A0307

Relative Jump Out of Range

The target of a relative jump is too far from the jump instruction to fit in a signed 8-bit offset.

Example

start:
    JR [far]
    .addr 0x0200
far:
    HALT

How to fix

Move the target closer or use an absolute jump.

JMP far

A0308

Scratch Register Conflict

A pseudo-instruction needs a scratch register that is also used as one of its operands. Expanding the instruction would overwrite that operand.

Example

MUL A, R1, R2

How to fix

Use a different operand register, or replace the pseudo-instruction with explicit core instructions that preserve the value.

MUL R3, R1, R2

A0309

Invalid Address Directive

An .addr directive targets an address below the current address. The assembler can pad forward, but it cannot move backward or overwrite bytes already emitted.

Example

.origin 0x1000
NOP
.addr 0x1001

How to fix

Choose a target at or above the current address.

.origin 0x1000
NOP
.addr 0x1002

A0310

Duplicate Constant

The same constant name is defined more than once. The diagnostic marks both definitions.

Example

.const @COLOR, 0x01
.const @COLOR, 0x02

How to fix

Keep one definition or give the constants distinct names.

.const @FOREGROUND, 0x01
.const @BACKGROUND, 0x02

A0311

Unknown Constant

An operand refers to a constant that has not been defined.

Example

LDI R1, @COLOR

How to fix

Define the constant or correct its spelling.

.const @COLOR, 0x01
LDI R1, @COLOR

A0312

Register Alias Preferred

A physical register name was used even though the register has a semantic alias. Aliases make the purpose of special registers clearer:

Example

LDI R0, 0x01

How to fix

Use the preferred alias instead of the physical register name.

LDI A, 0x01