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RENESAS TOOL NEWS on October 1, 2005: RSO-H8C-051001D
A Note on Using the C/C++ Compiler Package
V.6 for the H8SX, H8S, and H8 Families |
Please take note of the following problem in using the C/C++ compiler package V.6 for the H8SX, H8S, and H8 families:
- On accessing an incorrect addresses if a structure nested in another has members of a structure-type array (H8C-0026)
- Versions Concerned
The C/C++ compiler package for the H8SX, H8S, and H8 families
V.6.00 Release 00 through V.6.00 Release 03,
V.6.01 Release 00, and V.6.01 Release 01
- Description
If a structure is declared to be nested in another structure, and the structure-type variables of the former are declared to be of array type, incorrect addresses may be accessed.
| 2.1 |
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Conditions
This problem occurs if the following conditions are all satisfied:
| (1) | | The cpu=h8sxn, h8sxm, h8sxa, h8sxx, or ae5 option is used.
And also the cpu=2000n, 2600n, 2000a, or 2600a option is used
if the legacy=v4 option is not selected in the compiler package
V.6.01 Release 00 or later. |
| (2) | | A structure and its structure-type variables are declared. |
| (3) | | Structures nested in the structure in (2) in two or more levels
are declared, and the structure-type variables of the structure
in the deepest nesting level are declared to be an array type. |
| (4) | | The structures nested in (3) is not declared to be the first
member of the structure in (2). |
| (5) | | Dot operators are used for referencing or defining
structure-type variables. |
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| 2.2 |
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Example
----------------------------------------------------------
struct {
int data; // Condition (4)
struct { // Condition (3); 1st nesting
struct { // Condition (3); 2nd nesting
int a;
int b;
}x[2]; // Condition (3); Structure-type
// array nested in deepest level
}y;
}z; // Condition (2)
int v;
void func(int offset){
v = z.y.x[offset].a; // Condition (5)
}
---------------------------------------------------------- |
- Workaround
This problem can be circumvented either of the following ways:
| (1) |
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Declare the first structure nested in Condition (3) to be the first member of the structure in Condition (2).
Example:
----------------------------------------------------------
struct {
struct { // As 1st member of a structure,
use another
struct {
int a;
int b;
}x[2];
}y;
int data;
}z;
int v;
void func(int offset){
v = z.y.x[offset].a;
}
---------------------------------------------------------- |
| (2) |
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Use a pointer to access a structure-type variable.
Example:
----------------------------------------------------------
struct str{
int data;
struct {
struct {
int a;
int b;
}x[2];
}y;
}z;
int v;
void func(int offset){
struct str *p = &z; // Declare pointer-type variable
v = p y.x[offset].a; // Access variable using pointer
}
---------------------------------------------------------- |
- Schedule of Fixing the Problem
We will fix this problem in the next release of the product (in the first quarter of 2006).
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