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RENESAS TOOL NEWS on November 16, 2005: RSO-SHC-051116D
| Notes on Using the C/C++ Compiler Package V.9
for the SuperH RISC Engine Family of MCUs |
Please take note of the following problems in using the C/C++ compiler
package V.9 for the SuperH RISC engine family:
- On calling a function that takes arguments passed via the stack (SHC-0050)
- On using a union that contains two or more members of the same structure or union type (SHC-0051)
- Versions Concerned
The C/C++ compiler package for the SuperH RISC engine family
V.9.00 Release 00 through V.9.00 Release 03
- Descriptions
| 2.1 |
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On Calling a Function That Takes Arguments Passed via the Stack
(SHC-0050)
If an interrupt is generated after a function that takes arguments
passed via the stack is called, the value of the stack pointer pointing
to the beginning of the interrupt routine may become an odd number.
Conditions:
This problem may occur if the following conditions are all satisfied:
- The optimize=1 option is used.
- A call is made to a function that takes arguments passed via the stack.
- The total size of the arguments in Condition 2 is 124 bytes or more and 252 bytes or less.
Example:
----------------------------------------------
typedef struct {
char a[128];
} ST;
extern void f(ST fc);
ST a;
void func() {
f(a); // Conditions 2 and 3
}
----------------------------------------------
Result of compilation:
----------------------------------------------
_func:
STS.L PR,@-R15
ADD #-128,R15
MOV.L L11,R2 ; _a
MOV.L L11+4,R6 ; __slow_mvn
MOV #-128,R0 ; H'FFFFFF80
MOV R15,R1
JSR @R6
EXTU.B R0,R0
MOV.L L11+8,R1 ; _f
JSR @R1
NOP
ADD #127,R15 ; Value of stack pointer becomes odd
ADD #1,R15 ; If an interrupt generated immediately
; before this, value of stack pointer
; pointing to beginning of interrupt
; routine becomes odd
LDS.L @R15+,PR
RTS
NOP
----------------------------------------------
Workaround:
Use the optimize=0 option; not optimize=1.
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| 2.2 |
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On Using a Union That Contains Two or More Members of the Same
Structure or Union Type (SHC-0051)
If a union that contains two or more members of the same structure or
union type is used, the offset values of union members from the top of
the union may become incorrect.
Conditions:
This problem may occur if the following conditions are all satisfied:
- A union is used.
- The union in Condition 1 contains a structure- or union-type member.
- The union in Condition 1 contains other members of the same structure or union type as the member in Condition 2.
- The offset values of the members in Conditions 2 and 3 from the top of the union are the same.
- In the members in Conditions 2 and 3, members declared at the second or later are referenced or defined.
Example
----------------------------------------------
typedef struct {
unsigned int x;
} ST;
typedef union { // Condition 1
struct {
unsigned char a;
ST s2[1]; // Conditions 2 and 4
} st1;
struct {
unsigned char c;
ST s3; // Conditions 3 and 4
} st2;
} UN;
void func() {
volatile int a=0;
UN u;
f(u.st2.s3.x); // Condition 5
}
----------------------------------------------
Result of compilation:
----------------------------------------------
_func:
STS.L PR,@-R15
ADD #-12,R15
MOV.L L11+2,R2 ; _f
MOV.L @(4,R15),R4 ; Must be MOV.L @(8,R15),R4
MOV #0,R3
JSR @R2
MOV.L R3,@R15
ADD #12,R15
LDS.L @R15+,PR
RTS
NOP
----------------------------------------------
Workaround:
Define structures or unions that have names different from the
structure or union in Condition 2 above and contain the members of
the same names as its members. Then declare the members in Condition 3
to have the type of the structures or unions having different names.
Example:
----------------------------------------------------------
typedef struct {
unsigned int x;
} ST;
typedef struct {
unsigned int x;
} ST1;
typedef union {
struct {
unsigned char a;
ST s2[1];
} st1;
struct {
unsigned char c;
ST1 s3;
} st2;
} UN;
---------------------------------------------------------- |
- Schedule of Fixing the Problems
We plan to fix these problems in the next release of the product
(scheduled in the first quarter of 2006).
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