Re: [PATCH v4 09/15] gdb/testsuite: fix gdb.base/msym-bp-shl when running with Clang

[Bruno Larsen <blarsen@redhat.com>]

On 12/09/2022 12:58, Andrew Burgess wrote:
> Bruno Larsen via Gdb-patches <gdb-patches@sourceware.org> writes:
>
>> Because Clang's -O0 is not as unoptimized as gcc's, one of the functions
>> of gdb.base/msym-bp-shl was being optimized away, making the entire test
>> fail. A lot of the test fail like so:
>>
>> (gdb) break foo
>> Breakpoint 1 at 0x401030
>> (gdb) FAIL: gdb.base/msym-bp-shl.exp: debug=0: before run: break foo
>> info breakpoint
>> Num     Type           Disp Enb Address            What
>> 1       breakpoint     keep y   0x0000000000401030 <foo@plt>
>> (gdb) FAIL: gdb.base/msym-bp-shl.exp: debug=0: before run: info breakpoint
>>
>> As the test expects 2 breakpoints to be placed. This can't be easily fixed
>> by adding __attribute__ ((used)) to the function, since Clang will still
>> optimize away the function. Because of this, the test is skipped when
>> the it detects that Clang is being used
> In this mail:
>
>    https://sourceware.org/pipermail/gdb-patches/2022-March/187197.html
>
> Pedro suggests using __attribute__((used)), in your follow up:
>
>    https://sourceware.org/pipermail/gdb-patches/2022-March/187199.html
>
> you confirm that this approach works for you.  I just checked, and the
> attribute patch Pedro suggests makes the test pass for me with Clang.
>
> Should this patch have been updated?  If not, what changed?

This patch should have been updated, sorry.

--
Cheers,
Bruno

>
> Thanks,
> Andrew
>
>> ---
>>   gdb/testsuite/gdb.base/msym-bp-shl.exp | 8 ++++++++
>>   1 file changed, 8 insertions(+)
>>
>> diff --git a/gdb/testsuite/gdb.base/msym-bp-shl.exp b/gdb/testsuite/gdb.base/msym-bp-shl.exp
>> index 42adcb191dd..dd7d05bab52 100644
>> --- a/gdb/testsuite/gdb.base/msym-bp-shl.exp
>> +++ b/gdb/testsuite/gdb.base/msym-bp-shl.exp
>> @@ -22,6 +22,14 @@ if {[skip_shlib_tests]} {
>>       return 0
>>   }
>>   
>> +# Clang will optimize away the static foo, regardless of using
>> +# __attribute__((used)), so we'll always get a single breakpoint
>> +# making this test useless
>> +if {[test_compiler_info {clang-*-*}]} {
>> +    untested "Clang optimizes away one of the functions"
>> +    return
>> +}
>> +
>>   standard_testfile msym-bp-shl-main.c msym-bp-shl-main-2.c msym-bp-shl-lib.c
>>   set srcfile ${srcdir}/${subdir}/${srcfile}
>>   set srcfile2 ${srcdir}/${subdir}/${srcfile2}
>> -- 
>> 2.31.1