Aucbvax.2502
fa.unix-wizards
utzoo!decvax!ucbvax!naha@LL-ASG
Fri Jul 31 12:30:57 1981
bug in v7 C compiler
From: naha at LL-ASG (Mark Nahabedian)
The version 7 C compiler causes sign extension to be performed when one casts
an unsigned integer to a long when innitializing variables.
As a test, consider the source program
long a = (long) 0177777;
long b = (long) (unsigned int) 0177777;
long c = 0177777L;
long x;
int y = 0177777;
unsigned int z = 0177777;
foo()
{
x = (long) y;
x = (long) z;
}
which produces the assembler input
.globl _a
.data
_a:
177777; 177777
.globl _b
.data
_b:
177777; 177777
.globl _c
.data
_c:
0; 177777
.comm _x,4
.globl _y
.data
_y:
177777
.globl _z
.data
_z:
177777
.globl _foo
.text
_foo:
~~foo:
jsr r5,csv
jbr L1
L2:mov _y,2+_x
sxt _x
mov _z,2+_x
clr _x
L3:jmp cret
L1:jbr L2
.globl
.data
Note that in the case of actual assingmet at run-time it sign extends when
it should and doesn't when it shouldn't.
When it innitializes the variable b, it converts -1 integer to -1 long even
when it has been explicitly told that the -1 integer is really an unsigned
0177777 integer.
Any ideas about why it does this or how it could be fixed?
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