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RENESAS TOOL NEWS on June 1, 2005: RSO-M3T-NC308WA_2-050601D
A Note on Using
C-Compiler Package M3T-NC308WA
--On Referencing Array-Type Variables
Qualified with "const"-- |
Please take note of the following problem in using the M3T-NC308WA C-compiler package (this C-compiler package is used for the M32C/90, M32C/80 and M16C/80 series of MCUs):
- On referencing array-type variables qualified with "const"
- Versions Concerned
M3T-NC308WA V.5.00 Release 1 through V.5.20 Release 02
- Description
Referencing an array-type variable declared with "typedef" and qualified with "const" delivers a warning message at linking, and the executable file created will not run properly.
- 2.1 Conditions
- This problem occurs if the following conditions are all satisfied:
| (1) |
The type of an array-type variable is defined using the "typedef" specifier. |
| (2) |
The array-type variable in (1) is not qualified to be "const", "near", or "far". |
| (3) |
Then the array-type variable in (1) is declared outside a function, or declared inside a function using the "static" storage-class specifier. |
| (4) |
The array-type variable declared in (3) is qualified using the "const" qualifier; not "near", or "far". |
| (5) |
An element of the array-type variable in (3) is directly referenced using the array name. |
| (6) |
None of those compile options, -fconst_not_ROM(-fCNR), -ffar_RAM(-fFRAM), and -fnear_ROM(-fNROM), is selected. |
- 2.2 Example
-
-------------------------------------------------------------------
typedef char arr_t[2]; /* Conditions (1) and (2) */
const arr_t arr = { 0x11, 0x22 }; /* Conditions (3) and (4) */
char c;
void func(void)
{
c = arr[1]; /* Condition (5) */
}
-------------------------------------------------------------------
Warning message delivered at linking:
-------------------------------------------------------------------
a.c 7 Warning (ln308): a.r30 : 16-bits unsigned value is out of
range 0 -- 65535. address='fe0124'
-------------------------------------------------------------------
- Workaround
This problem can be circumvented in any of the following ways:
| (1) |
Don't declare the array-type variable qualified to be "const" using the "typedef" specifier.
Example
-------------------------------------------------------------
const char arr = { 0x11, 0x22 };
-------------------------------------------------------------
|
| (2) |
Declare the array-type variable qualified to be "const" by explicitly qualifying it as "far".
Example
-------------------------------------------------------------
const arr_t far arr = { 0x11, 0x22 };
-------------------------------------------------------------
|
| (3) |
Make the typedef declaration and the const type qualification of the array-type variable at the same time.
Example
-------------------------------------------------------------
typedef const char c_arr_t[2];
c_arr_t arr = { 0x11. 0x22 };
-------------------------------------------------------------
|
- Schedule of Fixing the Problem
We plan to fix this problem in the next release of the product.
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