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RENESAS TOOL NEWS on December 1, 2004: RSO-M3T-NC308WA-041201D
A Note on Using C-Compiler Packages
M3T-NC308WA and M3T-NC30WA
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Please take note of the following problem in using the M3T-NC308WA and M3T-NC30WA C-compiler packages:
- On using inline functions
- Products and Versions Concerned
M3T-NC308WA V.5.00 Release 1 and V.5.10 Release 1
(for the M32C/90, M32C/80 and M16C/80 series of MCUs)
M3T-NC30WA V.5.10 Release 1 and V.5.20 Release 1
(for the M16C/60, M16C/30, M16C/Tiny, M16C/20, M16C/10, and R8C/Tiny series of MCUs)
- Description
Incorrect code may be generated for the portion where a register variable is referenced within an inline function.
- Conditions
This problem occurs if the conditions stated in Pattern 1 or Pattern 2 below are all satisfied.
Pattern 1:
| (1) | A register variable is defined within an inline function. |
| (2) | An if construct exists in the inline function in (1). |
| (3) | Two or more assignment expressions to the register variable
in (1) exist in the inline function. Assume that one of these
expressions is A and one of the expressions placed after A is B. |
| (4) | Expression A is placed before the if construct. |
| (5) |
Expression B is placed only in the true or false statements of the if construct. |
| (6) | Any one or more of the compile options -O, -OS, and -OR are used. |
| (7) | Also compile option -fER is used. |
Example 1
-------------------------------------------------------------------
extern char a, b, c;
inline void func(void)
{
register int r = a; /* Conditions (1), (3) and (4) */
if (r < b) { /* Condition (2) */
r = b; /* Conditions (3) and (5) */
}
}
void testmain(void)
{
func();
}
-------------------------------------------------------------------
Pattern 2:
| (1) | A register variable is defined within an inline function. |
| (2) | Two or more assignment expressions to the register variable exist
in the inline function. Here, assume that one of these expressions is A and one of the expressions placed after A is B. |
| (3) | Between A and B is placed an assignment expression, C, to any other
than the register variable, whose right term is the same as B's. |
| (4) | Between C and B is referenced the register variable in (1). |
| (5) | Any one or more of the compile options -O, -O1, -O2, -O3, -O4, -O5,
-OR, and -OS are used. |
| (6) | Also compile option -fER is used. |
Example 2
-------------------------------------------------------------------
extern char aa, bb, xx, yy, zz;
inline void func(void) /* Condition (1) */
{
register char r; /* Condition (1) */
char s;
r = aa + 2; /* Condition (2) */
xx = bb + 1; /* Condition (3) */
s = r; /* Condition (4) */
r = bb + 1; /* Condition (2) */
yy = r;
zz = s;
}
void testmain(void)
{
func();
}
-------------------------------------------------------------------
- Workaround
This problem can be circumvented any of the following ways:
| (1) |
Don't declare a register variable. |
| (2) |
Don't use compile option -fER. |
| (3) |
Place a dummy asm function before referencing a register variable. |
Modification of Example 1:
-------------------------------------------------------------------
. . . . . . . . . . . . .
if (r < b) {
asm(); /* Place a dummy asm function */
r = b;
}
. . . . . . . . . . . . . .
-------------------------------------------------------------------
Modification of Example 2:
-------------------------------------------------------------------
. . . . . . . . . . . . . . . . .
inline void func(void)
{
register char r;
char s;
r = aa + 2;
xx = bb + 1;
s = r;
asm(); /* Place a dummy asm function */
r = bb + 1;
yy = r;
zz = s;
}
. . . . . . . . . . . . . . . . . .
-------------------------------------------------------------------
- Solution
This problem has already been fixed in the latest versions of the products,
the M3T-NC308WA V.5.20 Release 1 and the M3T-NC30WA V.5.30 Release 1.
So Please update yours to those online from
Software download for tools.
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