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

[Andrew Burgess <aburgess@redhat.com>]

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?

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