> For the complete documentation index, see [llms.txt](https://guide.cronuszen.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://guide.cronuszen.com/gpcscripting/gpc-script-guide/troubleshooting/high-value-compiler-errors.md).

# High-value compiler errors

### `GPC4001` — naming conflict

Variables, definitions, enum members, and const-data names share the data-symbol namespace:

```cpp
const uint8 strength[] = { 10, 20 };
int strength; // conflict
```

Function names, combo names, and function parameters use separate namespaces/scopes, although keywords and built-in names are still reserved.

Rename one symbol. Also avoid built-in function/constant names.

***

### `GPC4002` — undefined identifier

Check spelling, case, platform prefix, missing definition, and whether the name belongs to an internal/deprecated surface intentionally excluded from the guide.

***

### `GPC4003` — scoped variable unsupported

```cpp
main {
    int local_value; // invalid
}
```

Move runtime declarations to top level. Only function parameters are local.

***

### `GPC4018` — invalid const array structure

Every 2D row needs equal length:

```cpp
const uint8 BAD[][] = {
    { 1, 2, 3 },
    { 4, 5 }
};
```

***

### `GPC4020` / `GPC4021` — const index out of range

Indexes begin at zero. For size `N`, valid indexes are `0..N-1`.

***

### `GPC4022` / `GPC4023` — variable slot index under/overflow

Correct the runtime-array index or size/alias design. Validate dynamic indexes before access.

***

### `GPC4031` — missing second index

A 2D const array normally needs `[row][column]`, except valid address-style records.

***

### `GPC5102` — data not constant

Definitions, enum values, `data(...)`, const values, and array sizes cannot depend on runtime variables/functions.

***

### `GPC5106` — unsupported literal type

Declare strings in const data; do not pass a bare string where an integer/address expression is required.

***

### `GPC5125` — inconsistent return

Do not mix `return;` and `return value;` in the same function.

***

### `GPC5126` — invalid `addr`

Pass a const array/string/image/ADT item, not a runtime variable or arbitrary expression.

***

### `GPC5130..GPC5132` — built-in argument failure

Check argument count, required constant/variable form, exact accepted constant family, and numeric range against the function reference.

***

### `GPC5135` — unused required return

Consume the result:

```cpp
int value;
main { value = get_ival(PS5_RX); }
```

***

### `GPC5143` — variable limit exceeded

Live limit: 1,020 slots. Reduce runtime arrays, move immutable data to const arrays, and remove obsolete state.

***

### `GPC5144` — bytecode limit exceeded

Live maximum: 65,519 bytes. Measure before optimizing.

***

### `GPC5153` — argument outside hard range

Clamp/correct the source calculation. A runtime expression that might be out of range still needs explicit protection even when the compiler cannot prove it.


---

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