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Conference turris::decc

Title:	DECC
Notice:	General DEC C discussions
Moderator:	TLE::D_SMITHNTE

Created:	Fri Nov 13 1992
Last Modified:	Fri Jun 06 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	2212
Total number of notes:	11045

2089.0. "psect conflicting attributes" by DEVMKO::ESTRELLA () Tue Feb 11 1997 10:39

    I've got some code that was building fine until our machine was
    updated a few weeks ago.
    
	old DEC C      V4.0-000   
	new DEC C      V5.3-006
    
    	the old compile  command was
    
    $(CC) /STANDARD=VAXC/noopt/include=(sys$disk:[],
    dmq$user:, DECC$LIBRARY_include:,sys$library:) $(MMS$SOURCE)
    
    the new complie command is
    
     $(CC)
    /STANDARD=VAXC/noopt/extern_model=strict_refdef/include=(sys$disk:[],
    dmq$user:, DECC$LIBRARY_include:,sys$library:) $(MMS$SOURCE)
    
    
    I started getting a bunch of 
    
    psect conflicting attributes warnings
    
    and mulitiply define symbols warnings.
    
    This code I inherited has global vars in 2 modules with the same names
    and are referenced in other modules as externs.
    
    I've tried various switches and still can't quite get things linked.
    
    i've tried #pragma __extern_model __common_block __shr  
    
    /extern_module=strict_refdef
    
    Can anyone explain why the psect and multi defined warnings appeared?
    and what is the best way to correct this situation.
    
    thanks
    Dennis

T.R Title User Personal
Name Date Lines

2089.1 See Chap 4 of the User's Guide for detail on extern_model DECC::VMCCUTCHEON Tue Feb 11 1997 12:11 36

T.R	Title	User	Personal Name	Date	Lines
2089.1	See Chap 4 of the User's Guide for detail on extern_model	DECC::VMCCUTCHEON		`Tue Feb 11 1997 12:11`	36
	Hi, The command line you show for the old compiler appears to use the default extern model, relaxed_refdef, which tolerates multiple uninitialized definitions for the same object. The second command line you show for upgraded compiler, is specifying stict_refdef which limits you to exactly one definition. So depending on how and where you have placed your extern_model pragma directives, the multiple definition errors could be caused by that. Presumably you are aware that VAX C used the common block model, which is the most lax with regard to multiple definitions. Do track this down, I would suggest that you take a look at the DEC C User's Manual chap 4. I find the tables 4-5 through 4-8 at the end of the chapter to be the most helpful in explaining what psect information will be generated for each type of C declaration under the various extern models. I don't think that this is your problem, but beginning with V5.3, a new compiler-generated psect $READONLY_ADDR$ was added for static-exten const data that is initialized with link-time addresses. This allows $READONLY$ to remain sharable, where formally $READONLY$ would be marked as non-shared when that type of data was used. So possibly $READONLY$ was non-shared in the past. You will also find detailed information on PSECT "stuff" in the linker manual. I hope this helps, if not, you might wanna provide a small code example we can probably provide a more specific answer to your question. --val

Hi,

The command line you show for the old compiler appears
to use the default extern model, relaxed_refdef, which
tolerates multiple uninitialized definitions for the same
object.  The second command line you show for upgraded
compiler, is specifying stict_refdef which limits you to
exactly one definition.  So depending on how and where
you have placed your extern_model pragma directives,
the multiple definition errors could be caused by that.
Presumably you are aware that VAX C used the common block
model, which is the most lax with regard to multiple definitions.

Do track this down, I would suggest that you take a look
at the DEC C User's Manual chap 4.  I find the tables
4-5 through 4-8 at the end of the chapter to be the most
helpful in explaining what psect information will be generated
for each type of C declaration under the various extern models.

I don't think that this is your problem, but beginning with
V5.3, a new compiler-generated psect 
$READONLY_ADDR$ was added for static-exten const data 
that is initialized with link-time addresses.  This allows
$READONLY$ to remain sharable, where formally 
$READONLY$ would be marked as non-shared when 
that type of data was used.  So possibly $READONLY$
was non-shared in the past.

You will also find detailed information on PSECT "stuff"
in the linker manual.

I hope this helps, if not,
you might wanna provide a small code example we can probably 
provide a more specific answer to your question.

--val