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MAEC TOOL NEWS:
MAECT-M3T-NC308WA_3-030316D
A Note on Using C Compilers
M3T-NC308WA, M3T-NC30WA, M3T-NC79WA
and M3T-NC77WA
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Please take note of the following problem in using C compilers (with an assembler and integrated development environment) M3T-NC308WA, M3T-NC30WA, M3T-NC79WA, and M3T-NC77WA:
- On the standard library function "sprintf"
- Products and Versions Concerned
- For the M32C/80 and M16C/80 series MCUs
- M3T-NC308WA V.1.00 Release 1 through V.5.00 Release 1
- For the M16C/60, M16C/30, M16C/20, and M16C/10 series MCUs
- M3T-NC30WA V.1.00 Release 1 through V.5.00 Release 2
- For the 79xx series MCUs
- M3T-NC79WA V.2.00 Release 1 through V.4.10 Release 1A
- For the 77xx series MCUs
- M3T-NC77WA V.3.00 Release 1 through V.5.20 Release 4
- Description
If a space is inserted between two arguments, % and f, of the "sprintf" standard library function, the result of an assignment may become such a value as 0.000000. (The number of decimal places varies according to the specified format of the sprintf function.)
- Condition
This problem occurs if a floating-point number explained below is assigned to argument "f".
This floating-point number is such a value as 0.9999999, which can be rounded off to 1 as the nearest whole number.
- Example
-----------------------------------------------------------------------
#include <stdio.h>
float f;
int main( void )
{
char buf[10];
f = 0.9999999;
sprintf( buf,"% f",f ); /*A space inserted between % and f*/
}
-----------------------------------------------------------------------
In the above example, the value assigned to "buf" becomes 0.000000.
- Workaround
This problem can be circumvented in either of the following ways:
| (1) |
Modify the source file "print.c" of the standard library function as follows and re-create the standard library file by using the librarian:
Modification of "print.c":
To the processing in the _f8prn function, add the four lines with the comment of "Processing to add" as shown in an example below.
| Notes: | * This modification part begins at the 986th line in the M3T-NC308WA V.5.00 Release 1, and this beginning line varies according to compilers and their versions.
* The English version does not have any comments in the comment columns. |
--------------------------------------------------------------------
if ( CHK_KETA ) {
if ( (p_flg == 'e' || p_flg == 'E') && inte[0]=='9' ) {
/* %e 9 */
inte[0] = '1'; /* */
if ( CHK_EFUGO ) {
/* */
cnt--;
if ( !cnt )
/* */
CLR_EFUGO;
} else
cnt++;
} else {
for ( r=0; r<seisu; r++ ) {
if ( inte[r] == '9' )
inte[r] = '0';
else {
++inte[r];
break;
}
}
if ( r==seisu && r!=0) {
inte[seisu] = '1';
seisu++;
}
else if( seisu == 0){ /* Processing to add */
inte[seisu] = '1'; /* Processing to add */
seisu++; /* Processing to add */
} /* Processing to add */
}
}
--------------------------------------------------------------------
Re-create the standard library file by going through the following steps:
- Modify the print.c file saved in the SRCxx\lib directory under the directory where your product is installed. Here xx denotes the numerals in each product type.
- Re-create the standard library file using the makefile.dos file saved in the SRCxx\lib directory.
- Copy the re-created standard library file to the directory indicated by environment variable LIBxx.
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| (2) |
Pass the absolute value of a floating-point number to the sprintf function as its argument.
--------------------------------------------------------------------
#include <stdio.h>
#include <math.h> /* math.h included */
float f;
int main( void )
{
char buf[10];
f = 0.9999999;
/* The absolute value of a real number assigned
after the first line of the buffer */
/* No space inserted after % */
buf[0] = ' '; /* A space assigned to buf[0] */
sprintf( &buf[1],"%f",f ); /* The value of f assigned
following buf[1] */
}
--------------------------------------------------------------------
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- Schedule of Fixing the Problem
We plan to fix this problem in our next release of the products.
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