Conference vaxaxp::vmsnotes

538.0. "problems with shareable image on alpha " by GALVIA::FOX_F () Mon Apr 28 1997 05:55

This note was originally posted in ALPHANOTES and I moved it to here. 

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I am having a problem with shareable images on an application port from 
VAX to ALPHA. Maybe someone could help. I have tried to summarise the problem 
below. 

The code being ported was written in BASIC and MACRO. 

The BASIC code needs to be able to write to the PSECT TDB which is 
defined in MACRO and is part of the shareable image. 


! Basic file maps a PSECT named TDB 

MY_TEST.BAS 
-----------
	MAP ( TDB ) & 
		LONG 	TEST_LONG 

! Link option file for MY_test is as follows 

TESTOPT.OPT
-----------
MY$SHR.EXE/SHARE 

! Macro File defines the PSECT name TDB 

MY$DATA.MAR 
-----------
	.PSECT	TDB	PIC,USR,OVR,REL,GBL,SHR,NOEXE,RD,WRT,PAGE
INT_TDBADR::	.LONG	0		; DEFINE SYMBOL FOR TDB
	.END 
	

! Shareable image built from MY$DATA.OBJ 

MY$SHR.EXE 
----------
$ LINK/NONATIVE/SYSEXE/DEBUG/SYM/TRACE/MAP=MY$SHR.MAP - 
	/FULL/CROSS/SHAREABLE=MY$SHR.EXE - 
	  MY$DATA.OBJ +	MYSHR/OPT

! Shareable option file looks like this 
MYSHR.OPT
---------

PSECT_ATTR=TDB,SHR


! Build command file for all of the above 

$ BASIC /OPTIMIZE/WARN/LIST/CROSS/DEBUG/OBJ=MY_TEST.OBJ MY_TEST.BAS
$ MACRO /MIGRATE /OBJ=MY$DATA.OBJ MY$DATA.MAR 
$ LINK/NONATIVE/SYSEXE/DEBUG/SYM/TRACE/MAP=MY$SHR.MAP - 
	/FULL/CROSS/SHAREABLE=MY$SHR.EXE - 
	  MY$DATA.OBJ +	MYSHR/OPT
$ LINK/NONATIVE/SYSEXE/DEBUG/SYM/TRACE/MAP=MY_TEST.MAP/ - 
	FULL/CROSS/EXECUTEABLE=MY_TEST.EXE -
	 MY_TEST.OBJ + TESTOPT/OPT

----------------------------------------------------------------------

On the VAX when I look in the MAP files for MY_TEST and for MY$SHR the 
address for the TDB section are the same. On the ALPHA they are not. 

Can anyone point out what the attributes for the PSECTs should be for 
the ALPHA. 

I feel I should be using a symbol_vector in the myshr.opt file but 
if I use the Psect name (TDB) the linker tells me I have an undefined symbol.

I tried the suggestion from the ALPHANOTES file of 
symbol_vector=(TDB=psect, INT_TDBADR=data ) and that did not work either. 

If I compile and link the code against a .OLB that contains the 
TDB PSECT - the code works perfectly on the ALPHA it is only when the 
shareable image is used that problems arise. 



Thanks for any help. 

Regards, 
John. 

    

The default for most languages on OpenVMS Alpha is to not include
the SHR option (it is not needed in most cases).  Thus the
BASIC module TDB psect is different than the MACRO/Shareable image
psect.  BASIC will also pad the MAP of TDB to 16 bytes, so you
get the error

%LINK-E-SHRPSCLNG, Psect TDB has length of 16
        in module MY_TEST$MAIN file KGB$ROOT:[JUNK]MY_TEST.OBJ;1
        which exceeds length of 4 in shareable image
KGB$ROOT:[JUNK]MY$SHR.EXE;4
%LINK-E-NOIMGFIL, image file not created

So you have to do two things (along with the symbol_vector).
Make the value of SHR consistant between modules and Pad out the Macro
module TDB psect.   It might also help to align the MACRO psect
definition at an Octaword.

    
    Yes, thanks a lot - that did the trick.