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RENESAS TOOL NEWS on February 16, 2005: RSO-M3T-CC32R-050216D
A Note on Using C-Compiler Package
M3T-CC32R V.4.30 Release 00
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Please take note of the following problem in using C-compiler package
M3T-CC32R V.4.30 Release 00, which is used for the M32R family of MCUs:
- On setting the address value of an object containing a structure, array or union using the #pragma ADDRESS directive
- Product Concerned
M3T-CC32R V.4.30 Release 00
- Description
Consider that a #pragma ADDRESS directive is used for defining the address
of an object that is an array or structure; or a union that has members
of type array or structure.
If a member or element placed at any address except the beginning address
of the object is accessed (read or written) or referenced by an address
operator (&), incorrect code is generated using the address of the member
or element placed at the beginning of the object.
- 2.1 Conditions
- This problem occurs if the following conditions are satisfied:
| (1) |
Any of the following three objects is declared outside of a function:
(a) A structure
(b) An array
(c) A union having members of type array or structure |
| (2) |
A #pragma ADDRESS directive is used for defining the object in (1). |
| (3) |
For a member or element placed at any address except the beginning
address of the object, either of the following is performed:
(a) Accessing (reading or writing)
(b) Referencing by an address operator (&) |
- 2.2 Examples
-
Source file: sample1.c
----------------------------------------------------------------------
#pragma ADDRESS data1 0x10000 /* Condition (2) */
struct stg1 {
int a;
int b;
} data1; /* Condition (1)-(a) */
void func1(void)
{
data1.b = 3; /* Condition (3)-(a) */
}
----------------------------------------------------------------------
Source file: sample2.c
----------------------------------------------------------------------
#pragma ADDRESS data2 0x20000 /* Condition (2) */
short data2[10]; /* Condition (1)-(b) */
short *d2;
void func2(void)
{
d2 = &data2[3]; /* Condition (3)-(b) */
}
----------------------------------------------------------------------
Source file: sample3.c
----------------------------------------------------------------------
union utg3 {
double a[10];
struct {
int b;
double c[5];
} d;
} data3; /* Condition (1)-(c) */
#pragma ADDRESS data3 0x30000 /* Condition (2) */
void func3(int i)
{
data3.d.c[i] = /* Condition (3)-(a) */
data3.a[4]; /* Condition (3)-(a) */
}
----------------------------------------------------------------------
- Workaround
Access the object using the address cast to a pointer. It is convenient
to use macros shown in the examples below.
Modification of sample1.c
----------------------------------------------------------------------
#define data1 ( *(struct stg1*) 0x10000 ) /* Converted to macro */
struct stg1 {
int a;
int b;
} /* data1 */ ; /* Only stg1 declared; data1 commented out */
void func1(void)
{
data1.b = 3; /* Replaced by macro */
}
----------------------------------------------------------------------
Modification of sample2.c
----------------------------------------------------------------------
#define data2 ( (short *) 0x20000) /* Converted to macro */
/* short data2[10]; */ /* data2 commented out */
short *d2;
void func2(void)
{
d2 = &data2[3]; /* Replaced by macro */
}
----------------------------------------------------------------------
Modification of sample3.c
----------------------------------------------------------------------
union utg3 {
double a[10];
struct {
int b;
double c[5];
} d;
} /* data3 */ ; /* Only utg3 declared; data3 commented out */
#define data3 ( *(union utg3*) 0x30000 ) /* Converted to macro */
void func3(int i)
{
data3.d.c[i] = /* Replaced by macro */
data3.a[4]; /* Replaced by macro */
}
----------------------------------------------------------------------
- Schedule of Fixing the Problem
We plan to fix this problem in our next release of the product.
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