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RENESAS TOOL NEWS on January 16, 2004: RSO-M3T-CC32R-040116D
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A Note on Using Cross-Tool Kit M3T-CC32R
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Please take note of the following problem in using the M3T-CC32R cross-tool kit for the M32R family MCUs:
- On displaying a value less than 0.5 by using a formatted output function such as printf
- Versions Concerned
M3T-CC32R V.1.00 Release 1 through V.4.20 Release 1
- Description
An absolute value less than 0.5 may be displayed as "0." instead of the correct value "0"
(where the decimal point and fractions are not displayed).
- 2.1 Conditions
- This problem occurs if the following four conditions are satisfied:
| (1) |
A floating constant is displayed using the %f conversion specifier in a formatted output function
(printf, vprintf, fprintf, vfprintf, sprintf, or vsprintf).
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| (2) |
The precision in the output conversion specification is zero.
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| (3) |
The # flag (alternate form) is not used in the output conversion specification.
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| (4) |
The absolute value of the constant to display is less than 0.5 and greater than 0.0.
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- 2.2 Examples
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Source file:
-------------------------------------------------------------------
#include <stdio.h>
char bf1[32], bf2[32], bf3[32], bf4[32], bf5[32];
int main()
{
double x;
int prec;
/* Example Condition (4) satisfied */
x = 0.1; /* Condition (4) */
sprintf(bf1, "%4.0f\n", x); /* Conditions (1)--(3) */
/* Processing handling bf1 */
x = -0.4999; /* Condition (4) */
sprintf(bf2, "%3.0f\n", x); /* Conditions (1)--(3) */
/* Processing handling bf2 */
x = 0.064; /* Condition (4) */
prec = 0; /* Condition (2) */
sprintf(bf3, "%1.*f\n", prec, x); /* Conditions (1), and (3) */
/* Processing handling bf3 */
/* Example Condition (4) unsatisfied (no problem) */
x = 0.0; /* Condition (4) unsatisfied */
sprintf(bf4, "%5.0f\n", x); /* Conditions (1)--(3) */
/* Processing handling bf4 */
x = -0.5; /* Condition (4) unsatisfied */
sprintf(bf5, "%5.0f\n", x); /* Conditions (1)--(3) */
/* Processing handling bf5 */
return 0;
}
-------------------------------------------------------------------
Outputs of bf1, bf2, bf3, bf4, and bf5 in the above source file:
| |
Display |
Correct Display |
| bf1 |
" 0." |
" 0" |
| bf2 |
"-0." |
" -0" |
| bf3 |
"0." |
"0" |
| bf4 |
" 0" |
Same as left |
| bf5 |
" -1" |
Same as left |
- Workaround
This problem can be circumvented in either of the following methods:
| (1) |
Use a macro to round down an absolute value less than 0.5 to 0.0.
Modified example of the source file in 2.2:
-------------------------------------------------------------------
#include <stdio.h>
#define TRUNC00(x) ((-0.5<(x)&&(x)<+0.5)?0.0*(x):(x))
/* A macro to round down an absolute value
less than 0.5 to 0.0 defined */
char bf1[32], bf2[32], bf3[32], bf4[32], bf5[32];
int main()
{
double x;
int prec;
/* Example Condition (4) satisfied */
x = 0.1;
sprintf(bf1, "%4.0f\n", TRUNC00(x)); /* Macro used */
/* Processing handling bf1 */
x = -0.4999;
sprintf(bf2, "%3.0f\n", TRUNC00(x)); /* Macro used */
/* Processing handling bf2 */
x = 0.064;
prec = 0;
sprintf(bf3, "%1.*f\n", prec, TRUNC00(x)); /* Macro used */
/* Processing handling bf3 */
/* Example Condition (4) unsatisfied (no problem)
but the macro used for coordinative descriptions */
x = 0.0;
sprintf(bf4, "%5.0f\n", TRUNC00(x)); /* Macro used */
/* Processing handling bf4 */
x = -0.5;
sprintf(bf5, "%5.0f\n", TRUNC00(x)); /* Macro used */
/* Processing handling bf5 */
return 0;
}
-------------------------------------------------------------------
Outputs of bf1, bf2, bf3, bf4, and bf5 in the above source file
before and after modification by Method (1):
| |
Before |
After |
| bf1 |
" 0." |
" 0" |
| bf2 |
"-0." |
" -0" |
| bf3 |
"0." |
"0" |
| bf4 |
" 0" |
" 0" |
| bf5 |
" -1" |
" -1" |
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| (2) |
Use the # flag to display a floating value.
Using the # flag displays an absolute value greater than 0.5 as a decimal number,
so the same type of representation is available for displaying both absolute values greater and less than 0.5.
Modified example of the source file in 2.2:
-------------------------------------------------------------------
#include <stdio.h>
char bf1[32], bf2[32], bf3[32], bf4[32], bf5[32];
int main()
{
double x;
int prec;
/* Example Condition (4) satisfied */
x = 0.1;
sprintf(bf1, "%#4.0f\n", x); /* # flag used */
/* Processing handling bf1 */
x = -0.4999;
sprintf(bf2, "%#3.0f\n", x); /* # flag used */
/* Processing handling bf2 */
x = 0.064;
prec = 0;
sprintf(bf3, "%#1.*f\n", prec, x); /* # flag used */
/* Processing handling bf3 */
/* Example Condition (4) unsatisfied (no problem)
but the # flag used for coordinative descriptions */
x = 0.0;
sprintf(bf4, "%#5.0f\n", x); /* # flag used */
/* Processing handling bf4 */
x = -0.5;
sprintf(bf5, "%#5.0f\n", x); /* # flag used */
/* Processing handling bf5 */
return 0;
}
-------------------------------------------------------------------
Outputs of bf1, bf2, bf3, bf4, and bf5 in the above source file
before and after modification by Method (2):
| |
Before |
After |
| bf1 |
" 0." |
" 0." |
| bf2 |
"-0." |
"-0." |
| bf3 |
"0." |
"0." |
| bf4 |
" 0" |
" 0." |
| bf5 |
" -1" |
" -1." |
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- Schedule of Fixing the Problem
We plan to fix this problem in our next release of the product.
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