Actually, it looks like the compiler is generating correct code; it's just
that the debugger actually steps through several lines of instructions on
that single line
return 1;
This is what the disassembly looks like using opt 1:
UInt16 err;
00000000: 4E56 0000 link a6,#0
00000004: 2F03 move.l d3,-(a7)
err = 0;
if (err != 0)
00000006: 7600 moveq #0,d3
return 1;
else
return 0;
00000008: 6704 beq.s *+6 ; 0x0000000e
0000000A: 7001 moveq #1,d0
0000000C: 6002 bra.s *+4 ; 0x00000010
0000000E: 7000 moveq #0,d0
Viewing in Mixed mode in the debugger window, the debugger will reach
00000008: 6704 beq.s *+6 ; 0x0000000e
and then branch to
0000000E: 7000 moveq #0,d0
which returns 0 - exactly what was intended.
Rgds,
Jun-Kiat Lam
Metrowerks Technical Support
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of William
Brodie
Sent: Thursday, July 06, 2000 3:16 PM
To: Palm Developer Forum
Subject: CodeWarrior optimizer: incorrect code for simple conditionals
With the default optimization settings, CodeWarrior generates incorrect code
for simple conditional statements. (We observed the problem in CodeWarrior
Version 4.0.1, Build 0436 but have also tested it using the 3.5 SDK with
CodeWarrior 6.) The following sample produces the symptom:
#include <Pilot.h>
DWord PilotMain( Word cmd, Ptr cmdPBP, Word launchFlags)
{
UInt16 err;
err = 0;
if (err != 0)
return 1;
else
return 0;
}
With the default global optimization settings (optimize for speed, level 1),
this will cause PilotMain to bypass the test and return 1. With
optimization turned off (optimize for speed, level 0), it correctly returns
0. The project was created from a virgin "Palm VII Stationery" C project.
Of course, we can get rid of the problem by always compiling with
optimizations turned off, but that is undesirable. Is this a known problem?
It seems like a pretty basic one.
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