https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123915
Bug ID: 123915
Summary: [M68K][Fixed-Point] Compiler may generate wrong
overflow in conversion from 'double' to '_Accum'
Product: gcc
Version: 14.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: djipi.mari at gmail dot com
Target Milestone: ---
No matter what, the conversion will generate warnings, by examples:
test.c:676:14: warning: overflow in conversion from 'double' to '_Accum'
changes value from '-6.8000006999999998e+4' to '6.3071993011474609375e+4'
[-Woverflow]
676 | j4 = -68000.007;
| ^
test.c:682:14: warning: overflow in conversion from 'double' to '_Accum'
changes value from '-9.9999990000000002e+5' to '-6.5536e+4' [-Woverflow]
682 | j4 = -999999.9;
| ^
test.c:685:14: warning: overflow in conversion from 'double' to '_Accum'
changes value from '9.9999990000000002e+5' to 6.5535999969482421875e+4'
[-Woverflow]
685 | j4 = 999999.9;
| ^~~~~~~~
In the first case, the overflow value can be wrong, such as:
_Accum j4
j4 = -68000.007;
Will have a positive value of 63071.993.
For the second case, the conversion value seems right:
j4 = -999999.9;
Will have a negative value of -65536.000
For the third case, the conversion value seems right:
_Accum j4
j4 = 999999.9;
Will have a positive value of 65535.999
