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MAEC TOOL NEWS:
MAECT-NC77-020601D
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A note on C Compiler NC77
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Please take note of the following problem in using C compiler NC77 released before C compiler (with an assembler and integrated development environment) M3T-NC77WA for the 77xx series MCUs.
- Comparing the evaluation results of the right and left terms of a conditional operator, both of type singed long or unsigned long, may result in incorrect code being generated.
- Versions Concerned
NC77 V.3.00 Release 1 -- V.3.10 Release 2
- Description
- Comparing the evaluation results of the right and left terms of a conditional operator, both of type singed long or unsigned long, may result in the following incorrect code being generated:
- The comparison of the upper 2 bytes of a variable with those of another is replaced by the comparison of the lower 2 bytes of them.
- 2.1 Conditions
- This problem occurs if the C-language program satisfies all the conditions described in either Condition A or B below.
- Condition A
- (1) The evaluation results of the right and left terms of a conditional operator, both of type singed long or unsigned long, are compared. (The results of implicit conversions make valid comparisons, of course.)
- (2) A less than (<) or a greater than or equal to (=>) operator is used.
- (3) The term to the left of the above operator is an auto variable.
- (4) The term to the right of the above operator is such a value saved in a register as a function return value, an operation result, or a value pointed to by a pointer variable.
- Condition B
- (1) The evaluation results of the right and left terms of a conditional operator, both of type singed long or unsigned long, are compared. (The results of implicit conversions make valid comparisons, of course.)
- (2) A greater than (>) or a less than or equal to (<=) operator is used.
- (3) The term to the right of the above operator is an auto variable.
- (4) The term to the left of the above operator is such a value saved in a register as a function return value, an operation result, or a value pointed to by a pointer variable.
- 2.2 Example
[In Condition A]
-------------------------------------------------------------
int i, j;
long l;
if( l < (m + m) )
:
-------------------------------------------------------------
- Workaround
- If this symptom arises, temporarily save the value described in (4) of Condition A or B in an auto variable; then compare auto variables with each other.
[Example in Condition A]
-------------------------------------------------------------
int i, j;
long l;
long tmp;
tmp = m + n; /* Operation result saved in an auto variable */
if( l < tmp ) /* Comparison made between auto variables */
:
-------------------------------------------------------------
- Solution
Please use NC77 V.3.20 Release 1 or later.
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