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Re: [bug #41758] VMS Make incorrectly reports archives support present.

From: John E. Malmberg
Subject: Re: [bug #41758] VMS Make incorrectly reports archives support present.
Date: Sat, 14 Jun 2014 12:44:52 -0500
User-agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:17.0) Gecko/20130215 Thunderbird/17.0.3

On 6/10/2014 3:24 PM, h.becker wrote:
On 06/06/2014 05:15 AM, John Malmberg wrote:
lbr$set_module, the documentation says:

So the size of struct mhddef may not be enough and returning more than
that is not an error. Allocating LBR$C_MAXHDRSIZ bytes for the buffer is
probably the best one can do, because the contents of the fields
mhd$b_usrdat and cre$l_uhd is not known, here.

This issue is only present on older versions of VMS, not the current version, so someone else also considered it a bug and fixed it.

The library routine is given a descriptor that sets the bounds that it can write to, and there is a return status code to indicate when there is more data to be read, so that the call can be repeated with a larger buffer.

Length of the module header. The buflen argument is the address of a
longword receiving the length of the returned module header.

Will fix in the next patch submission. That bug was present in the original code also. This is why a prefer to hand construct the prototypes for the library routines and system services. I can set them up to force a compile time error in these cases.

We are saved from data corruption because the compiler does not tightly pack variables so 32 bits was available for the write. But this should get fixed.

So in arscan.c
"unsigned short buffer_length;  /* Actual buffer length */"
should be changed to a type of "unsigned int".

Regarding comments, I would like to have some comments like

/* On VMS, (object) modules in libraries do not have suffixes. That is,
    to find a match for a pattern, the pattern must not have any suffix.
    So the suffix from the pattern is saved and the pattern is stripped
    (ar_glob). If there is a match and the match, which is a module
    name, is added to the chain, the saved suffix is added back to
    construct a source filename (ar_glob_match). */

maybe in "ar.c" just prior to "struct ar_glob_state". I admit, I don't
know and didn't try to understand the code, so the above "constructed"
comment may not be correct. (And it seems that this comment style is
almost always used for block comments).

It is mostly correct and the next patch will have a similar comment. I do not think it only applies to object modules though.

In arscan.c, I suggest to use LBR$_HDRTRUNC instead of LIB_W_HDRTRUNC. A
"globalvalue unsigned int LBR$_HDRTRUNC;" replaces the "#define
LIB_W_HDRTRUNC 2525184" and the check changes to "if ((status !=
LBR$_HDRTRUNC) && ..."

Globalvalue is the right storage class for this declaration as per
definition LBR$_HDRTRUNC can change any time.   With resolving it at link
time and doing a fixup at activation time the code will get the correct
value even if it is changed. I agree, I don't expect it to be changed,
but having own #defines for VMS defined values looks wrong to me. And as
far as I can see there are no LBR$_<code> return codes defined in any of
the LBR header files and it seems unlikely that this will be changed
(sooner or later or at all) by VMS engineering.

VMS convention has always been to use these as compile time constants which means that once they are set, they are never changed for backwards compatibility.

globalvalue is only visible if VAXC compatibility is active, and turning on stricter ANSI compliance in the compiler turns it off. Turning on the stricter ANSI compliance finds bugs that VAX C compatibility ignores, so that is something that is desired.

While there is a ANSI compatible VMS extension to allow the equivalent of a globalvalue, it is a bit ugly to use.

And the compiler best optimizes as a constant, not as a global value that is not known until run time.

So with all that considered, just setting a constant missing from the header files seems the best solution.

As VAX C is only needed for building on VMS 5.5-1 and earlier, unless there is active builders for that old of VMS, I have been removing VAX C specific code as I update modules or converting it to ANSI compliance.

In tests/scripts/vms/library I suggest to remove the "universal" option
from the test script. For image libraries, librarian seems to be happy
with an image which is flagged as a shareable image no matter whether it
has a global symbol table or not. So there is no need to have one on VAX
but none on Alpha/I64; in other words on all VMS platforms I suggest to
either use a global symbol table or to use none.

I will look at doing that in a future patch. It appears that the UNIVERSAL qualifier is ignored by non-VAX, so is not causing a problem.


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