Re: [PATCH 01/11] gdb/testsuite: ignore Non-C-typedefs for gdb.cp/class2.exp

[Andrew Burgess <aburgess@redhat.com>]

Bruno Larsen via Gdb-patches <gdb-patches@sourceware.org> writes:

> When attempting to test gdb.cp/class2.exp using clang, it fails to
> prepare with the following error:
>
> Executing on host: clang++    -fdiagnostics-color=never -Wno-unknown-warning-option  -c -g -o /home/blarsen/Documents/fsf_build/gdb/testsuite/outputs/gdb.cp/class2/class20.o /home/blarsen/Documents/fsf_build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.cp/class2.cc    (timeout = 300)
> builtin_spawn -ignore SIGHUP clang++ -fdiagnostics-color=never -Wno-unknown-warning-option -c -g -o /home/blarsen/Documents/fsf_build/gdb/testsuite/outputs/gdb.cp/class2/class20.o /home/blarsen/Documents/fsf_build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.cp/class2.cc
> /home/blarsen/Documents/fsf_build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.cp/class2.cc:53:14: warning: anonymous non-C-compatible type given name for linkage purposes by typedef declaration; add a tag name here [-Wnon-c-typedef-for-linkage]
> typedef class {
>              ^
>               Dbase
> /home/blarsen/Documents/fsf_build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.cp/class2.cc:54:2: note: type is not C-compatible due to this member declaration
>  public:
>  ^~~~~~~
> /home/blarsen/Documents/fsf_build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.cp/class2.cc:58:3: note: type is given name 'Dbase' for linkage purposes by this typedef declaration
> } Dbase;
>   ^
> 1 warning generated.
> gdb compile failed, /home/blarsen/Documents/fsf_build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.cp/class2.cc:53:14: warning: anonymous non-C-compatible type given name for linkage purposes by typedef declaration; add a tag name here [-Wnon-c-typedef-for-linkage]
> typedef class {
>              ^
>               Dbase
> /home/blarsen/Documents/fsf_build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.cp/class2.cc:54:2: note: type is not C-compatible due to this member declaration
>  public:
>  ^~~~~~~
> /home/blarsen/Documents/fsf_build/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.cp/class2.cc:58:3: note: type is given name 'Dbase' for linkage purposes by this typedef declaration
> } Dbase;
>   ^
> 1 warning generated.
> UNTESTED: gdb.cp/class2.exp: failed to prepare
>
> This can be silenced by adding -Wno-non-c-typedef-for-linkage. The test
> shows no failures with this change.
> ---
>  gdb/testsuite/gdb.cp/class2.exp | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gdb/testsuite/gdb.cp/class2.exp b/gdb/testsuite/gdb.cp/class2.exp
> index 32f9dfc18a5..e1e4ad0fae6 100644
> --- a/gdb/testsuite/gdb.cp/class2.exp
> +++ b/gdb/testsuite/gdb.cp/class2.exp
> @@ -18,7 +18,7 @@ if { [skip_cplus_tests] } { return }
>  
>  standard_testfile .cc
>  
> -if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug c++}]} {
> +if {[prepare_for_testing "failed to prepare" $testfile $srcfile {debug c++ additional_flags=-Wno-non-c-typedef-for-linkage}]} {
>      return -1

I worry about just adding an extra flag like this.  GCC is happy enough
as it ignores unknown arguments, but some other compiler might be
unhappy.

Additionally, with earlier versions of clang++ (I tested 9.0.1) the new
flag isn't recognised, and actually causes the build to fail.

I wonder if we should look to something like gdb.cp/pr9167.exp for how
to solve this?  In that script we do this:

  set flags [list debug c++]
  if { [test_compiler_info gcc-*] && [gcc_major_version] >= 10 } {
      # Work around PR gcc/101452.
      lappend flags additional_flags=-fno-eliminate-unused-debug-types
  }

this might be a better model for how to add the flag.

Thanks,
Andrew