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wmcalc: Null-termitate display string when clearing.

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Often, the number currently being displayed has more than 10 digits.
However, when clearing the display, only the first 10 digits were cleared.
When a new number was entered, it would be prepended to any digits that
weren't cleared.  This behavior was invisible to the user, causing
incorrect calculations, e.g., Debian bug #564173:

1814 / 720 * 300 -> 7568.41111

But the correct answer is 755.833333.

The problem was that when the display was cleared, the string that stores
this number was not null-terminated.  Indeed, 1814 / 720 gives us
2.519444444 (6 4's), but only 2.51944444 (5 4's) is displayed.  When we
begin to multiply by 300, the final 4 remained, and so we really were
multiplying by 3004.
This commit is contained in:
Doug Torrance 2018-08-29 22:59:57 -04:00 committed by Carlos R. Mafra
parent 1d813d4434
commit ec62fab633
1 changed files with 2 additions and 0 deletions
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2
wmcalc/wmcalcfunc.c
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@ -63,6 +63,7 @@ void clearcalc(void) {
for (i=0; i < DISPSIZE; i++) { for (i=0; i < DISPSIZE; i++) {
DispString[i] = ' '; DispString[i] = ' ';
} }
DispString[DISPSIZE] = '\0';
OpFlag = ' '; OpFlag = ' ';
} /***** End of function clearcalc() *****************************/ } /***** End of function clearcalc() *****************************/
@ -94,6 +95,7 @@ void clearnum(void) {
for (i=0; i < DISPSIZE; i++) { for (i=0; i < DISPSIZE; i++) {
DispString[i] = ' '; DispString[i] = ' ';
} }
DispString[DISPSIZE] = '\0';
} /***** End of function clearnum() ******************************/ } /***** End of function clearnum() ******************************/