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MAEC TOOL NEWS:
MAECT-NC30WA-010816D
Please take note of the following problem in using C compiler NC30WA (with an assembler and integrated development environment) for the M16C/60 and M16C/20 series MCUs.
- On testing equality or inequality (== or !=) between a bit field greater than 2 bits and an immediate value of 0 (zero)
- Versions Concerned
NC30WA V.2.00 Release 1 -- V.4.00 Release 2
- Description
Testing equality or inequality of a bit field greater than 2 bits that is of type signed long or unsigned long with immediate value 0 (zero) may result in incorrect code being generated.
- Conditions
- This problem occurs if the following two conditions are satisfied:
- (1) There exists a bit field greater than 2 bits that is of type unsigned long or signed long, extending across a 16-bit word boundary.
- (2) Equality or inequality (== or !=) between a bit field satisfying condition (1) and immediate value 0 is tested in the conditional expression of a control statement (if, while, or for).
- Example
---------------------------------------------------------------
struct _BitF {
long b1:10; /* Condition (1) */
long b2:10;
long b2:12;
} bf;
void func(void)
{
if(bf.b2 != 0){ /* Condition (2) */
:
}
}
---------------------------------------------------------------
- Workaround
Assign the bit field concerned to a temporary variable, and then perform equality or inequality test of the variable and immediate value 0.
[Example of modification:]
---------------------------------------------------------------
void func(void){
unsigned long tmp;
tmp = bf.b2; // Assign a bit field to a temporary variable
if(tmp != 0){ // Inequality of the temporary variable with
// immediate value 0 tested
:
}
}
---------------------------------------------------------------
- Schedule of Fixing the Problem
We plan to fix this problem in our next release.
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