Hi Ulrich and community members,

>I assume the existing dummy assignment
 > int dummy = Barrier[0] + TestStrings[0] + TestStringsH[0] + TestStringsW[0];
> is optimized out on AIX for some reason?

> Does it work if you move "dummy" to be global variable,
> and/or make the Barrier and TestStrings* variable non-const?

Yes Ulrich. It works if we make variables non-const. Kindly see the output below.

gmake check RUNTESTFLAGS='gdb.base/examine-backward.exp CC_FOR_TARGET="/opt/freeware/bin/gcc" CXX_FOR_TARGET="/opt/freeware/bin/g++" CXXFLAGS_FOR_TARGET="-O0 -w -g -gdwarf -maix64" CFLAGS_FOR_TARGET="-O0 -w -g -gdwarf -maix64"'

gmake check-single……….
(gdb) set charset ASCII

(gdb) set print elements 20

(gdb) x/6s &TestStrings

0x110000158 <TestStrings>:      "ABCDEFGHIJKLMNOPQRST"...

0x11000016c <TestStrings+20>:   "UVWXYZ"

0x110000173 <TestStrings+27>:   ""

0x110000174 <TestStrings+28>:   ""

0x110000175 <TestStrings+29>:   "\343\201\273\343\201\222\343\201\273\343\201\222"

0x110000182 <TestStrings+42>:   "01234567890123456789"...

(gdb) x/-1xb…………………
                === gdb Summary ===

# of expected passes            70

# of unsupported tests          1

So shall we remove this const and create the git patch?

Please see the diff pasted below.

Thanks and regards,
Aditya.

diff --git a/gdb/testsuite/gdb.base/examine-backward.c b/gdb/testsuite/gdb.base/examine-backward.c

index 995dc6a0b78..354c2e2f323 100644

--- a/gdb/testsuite/gdb.base/examine-backward.c

+++ b/gdb/testsuite/gdb.base/examine-backward.c

@@ -36,11 +36,11 @@ literals.  The content of each array is the same as followings:

    TestStrings, to avoid showing garbage when we look for strings

    backwards from TestStrings.  */

-const unsigned char Barrier[] = {

+unsigned char Barrier[] = {

   0x00,

};

-const unsigned char TestStrings[] = {

+unsigned char TestStrings[] = {

   0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,

   0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 0x50,

   0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,

@@ -54,7 +54,7 @@ const unsigned char TestStrings[] = {

   0x00

};

-const short TestStringsH[] = {

+short TestStringsH[] = {

   0x0041, 0x0042, 0x0043, 0x0044, 0x0045, 0x0046, 0x0047, 0x0048,

   0x0049, 0x004a, 0x004b, 0x004c, 0x004d, 0x004e, 0x004f, 0x0050,

   0x0051, 0x0052, 0x0053, 0x0054, 0x0055, 0x0056, 0x0057, 0x0058,

@@ -67,7 +67,7 @@ const short TestStringsH[] = {

   0x0000

};

-const int TestStringsW[] = {

+int TestStringsW[] = {

   0x00000041, 0x00000042, 0x00000043, 0x00000044,

   0x00000045, 0x00000046, 0x00000047, 0x00000048,

   0x00000049, 0x0000004a, 0x0000004b, 0x0000004c,

From: Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
Date: Monday, 6 November 2023 at 5:26 PM
To: gdb-patches@sourceware.org <gdb-patches@sourceware.org>, Aditya Kamath1 <Aditya.Kamath1@ibm.com>
Cc: Sangamesh Mallayya <sangamesh.swamy@in.ibm.com>
Subject: Re: [PATCH]-Change gdb.base/examine-backwards.exp testcase for AIX

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

>Kindly let me know what you think. I know that we have some dummy variables
>that is used to negate a similar problem using clang with lto. But if we
>can produce something that works for both AIX GCC and other targets Clang
>with LTO it will be great, and we can create a patch.

I assume the existing dummy assignment
  int dummy = Barrier[0] + TestStrings[0] + TestStringsH[0] + TestStringsW[0];
is optimized out on AIX for some reason?

Does it work if you move "dummy" to be global variable,
and/or make the Barrier and TestStrings* variable non-const?

Bye,
Ulrich