Re: Fix max-depth test case for AIX.

[Andrew Burgess <aburgess@redhat.com>]

Aditya Kamath1 <Aditya.Kamath1@ibm.com> writes:

> Respected community members,
>
> Please find attached a patch. (See: 0001-Fix-max-depth-test-case-for-AIX.patch)
>
> This patch is a small fix to ensure max-depth test case is passing all test cases in AIX.
>
> In AIX, if in the main program the variables are unused then the linker optimises
> these variables and the dwarf will not have proper address to the same. Hence, we cannot access these
> variables.
>
> Breakpoint 1, main () at /current_gdb/binutils-gdb/gdb/testsuite/gdb.base/max-depth.c:231
> 231       return 0;
> (gdb) set print max-depth 0
> (gdb) p s1
> Cannot access memory at address 0xefffffff
> (gdb) FAIL: gdb.base/max-depth-c.exp: exp='s1': depth=0: p s1
> set print max-depth 1
> (gdb) p s1
> Cannot access memory at address 0xefffffff
> (gdb) FAIL: gdb.base/max-depth-c.exp: exp='s1': depth=1: p s1
> set print max-depth 2
> (gdb) p s1
> Cannot access memory at address 0xefffffff
>
> In the log above we can see the address getting assigned is incorrect.
>
> So, can we use this fix? The idea is just to stop the linker from optimizing unused varaibles out in AIX.  Let me know what you think.
>
> Have a nice day ahead.
>
> Thanks and regards,
> Aditya.
> From da0e236d30473eea91766e124d49a2256b7cf398 Mon Sep 17 00:00:00 2001
> From: Aditya Vidyadhar Kamath <Aditya.Kamath1@ibm.com>
> Date: Mon, 1 Apr 2024 03:12:29 -0500
> Subject: [PATCH] Fix max-depth test case for AIX.
>
> In AIX, if in the main program the variables are unused then the linker optimises
> these variables and the dwarf will not have proper address to the same. Hence we cannot access these
> variables.
>
> This patch is a fix to the same so that all the test case of max-depth can passs in AIX as well.
> ---
>  gdb/testsuite/gdb.base/max-depth.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/gdb/testsuite/gdb.base/max-depth.c b/gdb/testsuite/gdb.base/max-depth.c
> index fee5de5af34..e4b4459eed5 100644
> --- a/gdb/testsuite/gdb.base/max-depth.c
> +++ b/gdb/testsuite/gdb.base/max-depth.c
> @@ -228,5 +228,9 @@ struct V7 : virtual V4, virtual V5, virtual V6 { int v7 = 1; } v7;
>  int
>  main ()
>  {
> +  #ifdef _AIX
> +  s1.x = 0;
> +  #endif

Is it only `s1` that's a problem?  None of the other variables are used
either, and the they are all checked by the test.

Given what the test is doing I don't think there's any need for the
#ifdef, I'd suggest just adding a comment explaining why we need to
ensure the variables are referenced, and reference them.

Thanks,
Andrew


> +
>    return 0;
>  }
> -- 
> 2.41.0