Re: Weak globals -- C400-L

Joe,
Sounds like it may be time to open a Support incident with IBM (PMR) to get some clarification -- maybe it's a defect and they might accept it as an APAR that may eventually result in PTFs? :) And, you already have a nice simple little "test case" to submit with your PMR ... ;-)

Good luck,
Mark S. Waterbury

On Tuesday, April 2, 2019, 10:54:31 AM EDT, Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx> wrote:

Sadly, it's quite inconsistent.

This works in CRTSRVPGM:

// Compilation unit 2:

#include <stdio.h>

void foo() __attribute__((weak));
void foo()
{
printf("Foo called from compilation unit 2.\n");
}

I am able to create the service program and it looks like the symbols
resolved correctly. But before I test that, I tried to do CRTPGM with
the same modules (remember that TFOO1 has a proper main). That failed
with CPD5D03 and the listing showed that the TFOO2 definition was being
treated as a strong global.

So:

#pragma weak doesn't work in CRTSRVPGM or CRTPGM
__attribute__((weak)) works in CRTSRVPGM
Neither works in CRTPGM

Ugh. I'll try the service program in a moment, just to see if calling
routines resolve correctly.

On 4/2/2019 9:20 AM, Joe Pluta wrote:

It looks like the #pragma weak is just not working. Here's the
relevant CRTSRVPGM output:

5770SS1 V7R3M0 160422 MVXJP/TFOO    DEV       04/02
Module . . . . . . . . . . . : TFOO2
   Library . . . . . . . . . : MVXJP
   Bound . . . . . . . . . . : *YES
   Change date/time . . . . . :     04/02/19 07:39:13
   Teraspace storage enabled : *YES
   Storage model . . . . . . : *SNGLVL
       Number    Symbol      Ref
Identifier                                   Type      Scope Export
       00000025 Def foo__Fv Proc      Module Strong
       00000026 Ref         0000011C _C_SIGABRT_ctl_action Data

Note that foo__Fv in TFOO2 is identified as a strong export. That's
just not correct. It later conflicts with the foo__Fv from TFOO3 and
the service program is not created.

On 4/2/2019 9:12 AM, Joe Pluta wrote:

Nope - still getting CPD5D03.

On 4/2/2019 9:08 AM, Joe Pluta wrote:

Thanks Jon, that's the way I'll go if I can't figure anything else
out. As you probably guess, I don't like DUPPROC, especially since
as I read the documentation, weak should work.

The EXPORT(*ALL) is simply for testing, but I'm not sure how the
binder source would help. I'm not very versed in binder source, but
as far as I can tell all binder source does is order the exported
modules. How would it help when resolving duplicate symbols?

Oh wait. Maybe that's the problem! Maybe it's trying to export both
the weak and the strong. Ah, let me try that. If I add binder
source to only export main maybe that will work.

On 4/2/2019 8:53 AM, Jon Paris wrote:

Joe - I think dup proc is the only way to go. As to your comment
"and even then the order isn't _guaranteed_" that should be dealt
with by binder language/source instead of doing Export *All. That
guarantees the slot sequence.

Jon Paris

www.partner400.com
www.SystemiDeveloper.com

On Apr 2, 2019, at 8:43 AM, Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx>
wrote:

Has anybody successfully used the weak #pragma for a function?
I'm trying to create a service program with three modules: one
that references a function, one with that function defined weakly,
and one with the function defined strongly. In that scenario, I
should be able to combine the following:

Reference, weak: calls weak
Reference, strong: calls strong
Reference, weak, strong: calls strong
Reference only: won't compile

The best example code I found was in the AIX reference:

https://www.ibm.com/support/knowledgecenter/SSGH3R_13.1.0/com.ibm.xlcpp131.aix.doc/compiler_ref/prag_weak.html

From what I can tell, that same syntax should work in the ILE
compiler, so I created the following:

|// TFOO1.CPP #include <stdio.h> void foo(); int main() { foo(); }
// TFOO2.CPP #include <stdio.h> #pragma weak foo__Fv void foo() {
printf("Foo called from compilation unit 2\n"); } // TFOO3.CPP
#include <stdio.h> void foo() { printf("Foo called from
compilation unit 3\n"); } |

CRTSRVPGM TFOO MODULES(TFOO1 TFOO2 TFOO3) EXPORT(*ALL) fails with
CPD5D03, Definition supplied multiple times for symbol 'foo__Fv'.

I can get around it with OPTION(*DUPPROC) but then I have to be
very careful of the order of my modules in the MODULES keyword of
CRTSRVPGM (and even then the order isn't _guaranteed_). That also
would hide any cases of unintentional procedure duplication, so
I'd really like to get #pragma weak working.

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