testsuite: Add further zero size elt passing tests [PR102024]

Hi!

As discussed in PR102024, zero width bitfields might not be the only ones
causing ABI issues at least on mips, zero size arrays or (in C only) zero
sized (empty) structures can be problematic too.

The following patch adds some coverage for it too.

Tested on x86_64-linux with
make check-gcc check-g++ RUNTESTFLAGS='ALT_CC_UNDER_TEST=gcc ALT_CXX_UNDER_TEST=g++ --target_board=unix\{-m32,-m64\} compat.exp=pr102024*'
make check-gcc check-g++ RUNTESTFLAGS='ALT_CC_UNDER_TEST=clang ALT_CXX_UNDER_TEST=clang++ --target_board=unix\{-m32,-m64\} compat.exp=pr102024*'
with gcc/g++ 10.3 and clang 11.  Everything but (expectedly)
FAIL: gcc.dg/compat/pr102024 c_compat_x_tst.o-c_compat_y_alt.o execute 
FAIL: gcc.dg/compat/pr102024 c_compat_x_alt.o-c_compat_y_tst.o execute 
for -m64 ALT_CC_UNDER_TEST=gcc passes.

Ok for trunk?

2022-03-31  Jakub Jelinek  <jakub@redhat.com>

	PR target/102024
	* gcc.dg/compat/pr102024_test.h: Add further tests with zero sized
	structures and arrays.
	* g++.dg/compat/pr102024_test.h: Add further tests with zero sized
	arrays.


	Jakub

On Thu, 31 Mar 2022, Jakub Jelinek wrote:

> Hi!
> 
> As discussed in PR102024, zero width bitfields might not be the only ones
> causing ABI issues at least on mips, zero size arrays or (in C only) zero
> sized (empty) structures can be problematic too.
> 
> The following patch adds some coverage for it too.
> 
> Tested on x86_64-linux with
> make check-gcc check-g++ RUNTESTFLAGS='ALT_CC_UNDER_TEST=gcc ALT_CXX_UNDER_TEST=g++ --target_board=unix\{-m32,-m64\} compat.exp=pr102024*'
> make check-gcc check-g++ RUNTESTFLAGS='ALT_CC_UNDER_TEST=clang ALT_CXX_UNDER_TEST=clang++ --target_board=unix\{-m32,-m64\} compat.exp=pr102024*'
> with gcc/g++ 10.3 and clang 11.  Everything but (expectedly)
> FAIL: gcc.dg/compat/pr102024 c_compat_x_tst.o-c_compat_y_alt.o execute 
> FAIL: gcc.dg/compat/pr102024 c_compat_x_alt.o-c_compat_y_tst.o execute 
> for -m64 ALT_CC_UNDER_TEST=gcc passes.
> 
> Ok for trunk?

OK.

> 2022-03-31  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR target/102024
> 	* gcc.dg/compat/pr102024_test.h: Add further tests with zero sized
> 	structures and arrays.
> 	* g++.dg/compat/pr102024_test.h: Add further tests with zero sized
> 	arrays.
> 
> --- gcc/testsuite/gcc.dg/compat/pr102024_test.h.jj	2022-03-24 12:24:41.625100842 +0100
> +++ gcc/testsuite/gcc.dg/compat/pr102024_test.h	2022-03-31 17:36:33.486710917 +0200
> @@ -4,3 +4,9 @@ T(2,int:0;float a;,F(2,a,2.25f,16.5f))
>  T(3,double a;long long:0;double b;,F(3,a,42.0,43.125)F(3,b,-17.5,35.75))
>  T(4,double a;long long:0;,F(4,a,1.0,17.125))
>  T(5,long long:0;double a;,F(5,a,2.25,16.5))
> +T(6,float a;struct{}b;float c;,F(6,a,42.0f,43.125f)F(6,c,-17.5f,35.75f))
> +T(7,float a;struct{}b[0];;,F(7,a,1.0f,17.125f))
> +T(8,int a[0];float b;,F(8,b,2.25f,16.5f))
> +T(9,double a;long long b[0];double c;,F(9,a,42.0,43.125)F(9,c,-17.5,35.75))
> +T(10,double a;struct{}b;,F(10,a,1.0,17.125))
> +T(11,struct{}a[0];double b;,F(11,b,2.25,16.5))
> --- gcc/testsuite/g++.dg/compat/pr102024_test.h.jj	2022-03-24 12:24:41.625100842 +0100
> +++ gcc/testsuite/g++.dg/compat/pr102024_test.h	2022-03-31 17:37:30.763877562 +0200
> @@ -4,3 +4,9 @@ T(2,int:0;float a;,F(2,a,2.25f,16.5f))
>  T(3,double a;long long:0;double b;,F(3,a,42.0,43.125)F(3,b,-17.5,35.75))
>  T(4,double a;long long:0;,F(4,a,1.0,17.125))
>  T(5,long long:0;double a;,F(5,a,2.25,16.5))
> +T(6,float a;struct{}b[0];float c;,F(6,a,42.0f,43.125f)F(6,c,-17.5f,35.75f))
> +T(7,float a;struct{}b[0];;,F(7,a,1.0f,17.125f))
> +T(8,int a[0];float b;,F(8,b,2.25f,16.5f))
> +T(9,double a;long long b[0];double c;,F(9,a,42.0,43.125)F(9,c,-17.5,35.75))
> +T(10,double a;struct{}b[0];,F(10,a,1.0,17.125))
> +T(11,struct{}a[0];double b;,F(11,b,2.25,16.5))
> 
> 	Jakub
> 
>

On 3/31/2022 9:54 AM, Jakub Jelinek via Gcc-patches wrote:
> Hi!
>
> As discussed in PR102024, zero width bitfields might not be the only ones
> causing ABI issues at least on mips, zero size arrays or (in C only) zero
> sized (empty) structures can be problematic too.
>
> The following patch adds some coverage for it too.
>
> Tested on x86_64-linux with
> make check-gcc check-g++ RUNTESTFLAGS='ALT_CC_UNDER_TEST=gcc ALT_CXX_UNDER_TEST=g++ --target_board=unix\{-m32,-m64\} compat.exp=pr102024*'
> make check-gcc check-g++ RUNTESTFLAGS='ALT_CC_UNDER_TEST=clang ALT_CXX_UNDER_TEST=clang++ --target_board=unix\{-m32,-m64\} compat.exp=pr102024*'
> with gcc/g++ 10.3 and clang 11.  Everything but (expectedly)
> FAIL: gcc.dg/compat/pr102024 c_compat_x_tst.o-c_compat_y_alt.o execute
> FAIL: gcc.dg/compat/pr102024 c_compat_x_alt.o-c_compat_y_tst.o execute
> for -m64 ALT_CC_UNDER_TEST=gcc passes.
>
> Ok for trunk?
>
> 2022-03-31  Jakub Jelinek  <jakub@redhat.com>
>
> 	PR target/102024
> 	* gcc.dg/compat/pr102024_test.h: Add further tests with zero sized
> 	structures and arrays.
> 	* g++.dg/compat/pr102024_test.h: Add further tests with zero sized
> 	arrays.
I'd generally lean towards a new test rather than extending an existing 
one, but that's a nit that primarily helps automated testing find 
regressions, so I wouldn't consider it a requirement to break out the 
new cases.

OK as-is or with the new cases in their own testfile.

jeff