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From: beard@ux5.lbl.gov (Patrick C Beard)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Think C chokes on assembler macro, help!
Message-ID: <6530@helios.ee.lbl.gov>
Date: 17 Aug 90 05:12:35 GMT
References: <4225@dogie.macc.wisc.edu>
Sender: usenet@helios.ee.lbl.gov
Reply-To: beard@ux5.lbl.gov (Patrick C Beard)
Organization: Berkeley Systems, Inc.
Lines: 51
X-Local-Date: 16 Aug 90 22:12:35 PDT

In article <4225@dogie.macc.wisc.edu> yahnke@vms.macc.wisc.edu (Ross Yahnke, MACC) writes:
#There is this nifty little routine in the MacTech Journal that
#decribes how to write a Think C macro to call an assembly routine
#that will pop the state of a handle onto the stack and then lock
#the handle. Also described is the corresponding routine to pop
#the state back off the stack. I can't get it to compile.
#
#The macro is:
#    #define _PushLock(H) asm  \
#    { move.l        H,a0      \
#      _HGetState              \
#      move.b        d0,-(sp)  \
#      move.l        H,a0      \
#      _HLock                  \
#    } /* PushLock */
#
#My C call is:
#    _PushLock((*Major)->Contrived.Complex.aHandle);
#
#Think C chokes when compiling/assembling the above line with
#the message "Pointer is required". This is presumably occuring
#when it tries to assemble:
#    move.l        (*Major)->Contrived.Complex.aHandle,a0

Think about what this means.  What addressing mode could possibly be
used to generate the correct code with all of these dereferences?  You
are mixing C and assembly a little TOO freely.  The only way this macro
can work is if you use a temporary which is on the stack, or in a register.

Now, this version will work whatever you pass it:

#define _PushLock(H)          \
    { Handle temp = H;        \
     asm {                    \
       move.l        temp,a0  \
      _HGetState              \
      move.b        d0,-(sp)  \
      move.l        temp,a0   \
      _HLock                  \
    }} /* PushLock */

It works because you force all the complicated addressing to happen automatic-
ally and the compiler does all the work.  temp is always relative to A6.

I hope this helps.

--
-------------------------------------------------------------------------------
-  Patrick Beard, Macintosh Programmer                        (beard@lbl.gov) -
-  Berkeley Systems, Inc.  ".......<dead air>.......Good day!" - Paul Harvey  -
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