andy@nthropy.UUCP (Andy Lowe) (01/24/91)
Dear X server hackers, My copy of the ANSI C spec says that when right shifting E1 >> E2, "If E1 has a signed type, whether the right shift is logical (fill with zeros) or arithmetic (fill with a copy of the sign bit) is implementation-defined." (section 3.3.7) Consider the following fragment of code from the MIARCOCTANTSHIFT macro in mizerarc.h ... d = b - (a >> 1) - d + (k3 >> 3); \ ... this is called out from the cfb arc drawing routines. Note that variable a can be negative. I have the misfortune to be running on an architecture without an arithmetic right shift instruction, and so my compiler has exercised it's "implementation-defined" option. In the interests of portability, can someone arrange to fix this apparent ANSI non-compliance in the standard distribution? I'm using R4. Perhaps it is already fixed in R5. Does anybody know? many thanks. Andy Lowe andy@nth.com
Nagesh_Pabbisetty.Henr801C@xerox.COM (01/24/91)
I am glad(?) to see that I am not the only one who feels that way. I got bitten by this in the arc drawing code. It took us quite a while to locate and change it. - nagesh (pabbiset@arisia.xerox.com) ------------------------------------------------------------------------------- Intelnet: 8*227-5458 MaBell: (716)427-5458 XNS : pabbisetty:henr801c:xerox Snail Mail: Arpa : pabbiset@arisia.xerox.com 1350 Jefferson Road, 801-27C, Rochester, NY 14623. -------------------------------------------------------------------------------
Nagesh_Pabbisetty.Henr801C@xerox.COM (01/24/91)
Dear X server hackers,
My copy of the ANSI C spec says that when right shifting E1 >> E2, "If
E1 has a signed type, whether the right shift is logical (fill with
zeros) or arithmetic (fill with a copy of the sign bit) is
implementation-defined." (section 3.3.7)
Consider the following fragment of code from the MIARCOCTANTSHIFT macro
in mizerarc.h
...
d = b - (a >> 1) - d + (k3 >> 3); \
...
this is called out from the cfb arc drawing routines. Note that
variable a can be negative.
I have the misfortune to be running on an architecture without an
arithmetic right shift instruction, and so my compiler has exercised
it's "implementation-defined" option.
In the interests of portability, can someone arrange to fix this
apparent ANSI non-compliance in the standard distribution? I'm using
R4. Perhaps it is already fixed in R5. Does anybody know?
many thanks.
Andy Lowe
andy@nth.com
I am glad(;-) to see that I am not the only one who feels that way.
I got bitten by this in the arc drawing code.
It took us quite a while to locate and change right shifts to divides (:-(
- nagesh (pabbiset@arisia.xerox.com)
-------------------------------------------------------------------------------
Intelnet: 8*227-5458 MaBell: (716)427-5458
XNS : pabbisetty:henr801c:xerox Snail Mail:
Arpa : pabbiset@arisia.xerox.com 1350 Jefferson Road, 801-27C,
Rochester, NY 14623.
-------------------------------------------------------------------------------