[PATCH] libstdc++: mark variables as possibly unused

Fri Aug 28 06:40:20 GMT 2020

>Test suite confirmation:
>All tests pass. Tested on both Manjaro and some Ubuntu 18.04 with gcc10
and gcc8 respectively.

Jonathan, one more thing. I hope it's what you asked for cause all I did
was:
make bootstrap
make check

On Fri, 28 Aug 2020 at 08:32, Krystian Kuźniarek <
krystian.kuzniarek@gmail.com> wrote:

> Ok, so here it is.
> New diff:
>
> diff --git a/libstdc++-v3/include/bits/atomic_base.h b/libstdc++-v3/include/bits/atomic_base.h
> index 015acef83c4..c4a763aae5c 100644
> --- a/libstdc++-v3/include/bits/atomic_base.h
> +++ b/libstdc++-v3/include/bits/atomic_base.h
> @@ -231,7 +231,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      _GLIBCXX_ALWAYS_INLINE void
>      clear(memory_order __m = memory_order_seq_cst) noexcept
>      {
> -      memory_order __b = __m & __memory_order_mask;
> +      memory_order __b __attribute__ ((__unused__))
> +        = __m & __memory_order_mask;
>        __glibcxx_assert(__b != memory_order_consume);
>        __glibcxx_assert(__b != memory_order_acquire);
>        __glibcxx_assert(__b != memory_order_acq_rel);
> @@ -242,7 +243,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      _GLIBCXX_ALWAYS_INLINE void
>      clear(memory_order __m = memory_order_seq_cst) volatile noexcept
>      {
> -      memory_order __b = __m & __memory_order_mask;
> +      memory_order __b __attribute__ ((__unused__))
> +        = __m & __memory_order_mask;
>        __glibcxx_assert(__b != memory_order_consume);
>        __glibcxx_assert(__b != memory_order_acquire);
>        __glibcxx_assert(__b != memory_order_acq_rel);
> @@ -416,7 +418,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        _GLIBCXX_ALWAYS_INLINE void
>        store(__int_type __i, memory_order __m = memory_order_seq_cst) noexcept
>        {
> -	memory_order __b = __m & __memory_order_mask;
> +	memory_order __b __attribute__ ((__unused__))
> +	  = __m & __memory_order_mask;
>  	__glibcxx_assert(__b != memory_order_acquire);
>  	__glibcxx_assert(__b != memory_order_acq_rel);
>  	__glibcxx_assert(__b != memory_order_consume);
> @@ -428,7 +431,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        store(__int_type __i,
>  	    memory_order __m = memory_order_seq_cst) volatile noexcept
>        {
> -	memory_order __b = __m & __memory_order_mask;
> +	memory_order __b __attribute__ ((__unused__))
> +	  = __m & __memory_order_mask;
>  	__glibcxx_assert(__b != memory_order_acquire);
>  	__glibcxx_assert(__b != memory_order_acq_rel);
>  	__glibcxx_assert(__b != memory_order_consume);
> @@ -439,7 +443,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        _GLIBCXX_ALWAYS_INLINE __int_type
>        load(memory_order __m = memory_order_seq_cst) const noexcept
>        {
> -	memory_order __b = __m & __memory_order_mask;
> +	memory_order __b __attribute__ ((__unused__))
> +	  = __m & __memory_order_mask;
>  	__glibcxx_assert(__b != memory_order_release);
>  	__glibcxx_assert(__b != memory_order_acq_rel);
>
> @@ -449,7 +454,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        _GLIBCXX_ALWAYS_INLINE __int_type
>        load(memory_order __m = memory_order_seq_cst) const volatile noexcept
>        {
> -	memory_order __b = __m & __memory_order_mask;
> +	memory_order __b __attribute__ ((__unused__))
> +	  = __m & __memory_order_mask;
>  	__glibcxx_assert(__b != memory_order_release);
>  	__glibcxx_assert(__b != memory_order_acq_rel);
>
> @@ -475,8 +481,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        compare_exchange_weak(__int_type& __i1, __int_type __i2,
>  			    memory_order __m1, memory_order __m2) noexcept
>        {
> -	memory_order __b2 = __m2 & __memory_order_mask;
> -	memory_order __b1 = __m1 & __memory_order_mask;
> +	memory_order __b2 __attribute__ ((__unused__))
> +	  = __m2 & __memory_order_mask;
> +	memory_order __b1 __attribute__ ((__unused__))
> +	  = __m1 & __memory_order_mask;
>  	__glibcxx_assert(__b2 != memory_order_release);
>  	__glibcxx_assert(__b2 != memory_order_acq_rel);
>  	__glibcxx_assert(__b2 <= __b1);
> @@ -490,8 +498,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  			    memory_order __m1,
>  			    memory_order __m2) volatile noexcept
>        {
> -	memory_order __b2 = __m2 & __memory_order_mask;
> -	memory_order __b1 = __m1 & __memory_order_mask;
> +	memory_order __b2 __attribute__ ((__unused__))
> +	  = __m2 & __memory_order_mask;
> +	memory_order __b1 __attribute__ ((__unused__))
> +	  = __m1 & __memory_order_mask;
>  	__glibcxx_assert(__b2 != memory_order_release);
>  	__glibcxx_assert(__b2 != memory_order_acq_rel);
>  	__glibcxx_assert(__b2 <= __b1);
> @@ -520,8 +530,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        compare_exchange_strong(__int_type& __i1, __int_type __i2,
>  			      memory_order __m1, memory_order __m2) noexcept
>        {
> -	memory_order __b2 = __m2 & __memory_order_mask;
> -	memory_order __b1 = __m1 & __memory_order_mask;
> +	memory_order __b2 __attribute__ ((__unused__))
> +	  = __m2 & __memory_order_mask;
> +	memory_order __b1 __attribute__ ((__unused__))
> +	  = __m1 & __memory_order_mask;
>  	__glibcxx_assert(__b2 != memory_order_release);
>  	__glibcxx_assert(__b2 != memory_order_acq_rel);
>  	__glibcxx_assert(__b2 <= __b1);
> @@ -535,8 +547,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  			      memory_order __m1,
>  			      memory_order __m2) volatile noexcept
>        {
> -	memory_order __b2 = __m2 & __memory_order_mask;
> -	memory_order __b1 = __m1 & __memory_order_mask;
> +	memory_order __b2 __attribute__ ((__unused__))
> +	  = __m2 & __memory_order_mask;
> +	memory_order __b1 __attribute__ ((__unused__))
> +	  = __m1 & __memory_order_mask;
>
>  	__glibcxx_assert(__b2 != memory_order_release);
>  	__glibcxx_assert(__b2 != memory_order_acq_rel);
> @@ -736,7 +750,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        store(__pointer_type __p,
>  	    memory_order __m = memory_order_seq_cst) noexcept
>        {
> -        memory_order __b = __m & __memory_order_mask;
> +        memory_order __b __attribute__ ((__unused__))
> +          = __m & __memory_order_mask;
>
>  	__glibcxx_assert(__b != memory_order_acquire);
>  	__glibcxx_assert(__b != memory_order_acq_rel);
> @@ -749,7 +764,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        store(__pointer_type __p,
>  	    memory_order __m = memory_order_seq_cst) volatile noexcept
>        {
> -	memory_order __b = __m & __memory_order_mask;
> +	memory_order __b __attribute__ ((__unused__))
> +	  = __m & __memory_order_mask;
>  	__glibcxx_assert(__b != memory_order_acquire);
>  	__glibcxx_assert(__b != memory_order_acq_rel);
>  	__glibcxx_assert(__b != memory_order_consume);
> @@ -760,7 +776,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        _GLIBCXX_ALWAYS_INLINE __pointer_type
>        load(memory_order __m = memory_order_seq_cst) const noexcept
>        {
> -	memory_order __b = __m & __memory_order_mask;
> +	memory_order __b __attribute__ ((__unused__))
> +	  = __m & __memory_order_mask;
>  	__glibcxx_assert(__b != memory_order_release);
>  	__glibcxx_assert(__b != memory_order_acq_rel);
>
> @@ -770,7 +787,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        _GLIBCXX_ALWAYS_INLINE __pointer_type
>        load(memory_order __m = memory_order_seq_cst) const volatile noexcept
>        {
> -	memory_order __b = __m & __memory_order_mask;
> +	memory_order __b __attribute__ ((__unused__))
> +	  = __m & __memory_order_mask;
>  	__glibcxx_assert(__b != memory_order_release);
>  	__glibcxx_assert(__b != memory_order_acq_rel);
>
> @@ -797,8 +815,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  			      memory_order __m1,
>  			      memory_order __m2) noexcept
>        {
> -	memory_order __b2 = __m2 & __memory_order_mask;
> -	memory_order __b1 = __m1 & __memory_order_mask;
> +	memory_order __b2 __attribute__ ((__unused__))
> +	  = __m2 & __memory_order_mask;
> +	memory_order __b1 __attribute__ ((__unused__))
> +	  = __m1 & __memory_order_mask;
>  	__glibcxx_assert(__b2 != memory_order_release);
>  	__glibcxx_assert(__b2 != memory_order_acq_rel);
>  	__glibcxx_assert(__b2 <= __b1);
> @@ -812,8 +832,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>  			      memory_order __m1,
>  			      memory_order __m2) volatile noexcept
>        {
> -	memory_order __b2 = __m2 & __memory_order_mask;
> -	memory_order __b1 = __m1 & __memory_order_mask;
> +	memory_order __b2 __attribute__ ((__unused__))
> +	  = __m2 & __memory_order_mask;
> +	memory_order __b1 __attribute__ ((__unused__))
> +	  = __m1 & __memory_order_mask;
>
>  	__glibcxx_assert(__b2 != memory_order_release);
>  	__glibcxx_assert(__b2 != memory_order_acq_rel);
> diff --git a/libstdc++-v3/include/ext/new_allocator.h b/libstdc++-v3/include/ext/new_allocator.h
> index 131718b8b2f..2e21a98409f 100644
> --- a/libstdc++-v3/include/ext/new_allocator.h
> +++ b/libstdc++-v3/include/ext/new_allocator.h
> @@ -117,7 +117,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>
>        // __p is not permitted to be a null pointer.
>        void
> -      deallocate(_Tp* __p, size_type __t)
> +      deallocate(_Tp* __p, size_type __t __attribute__ ((__unused__)))
>        {
>  #if __cpp_aligned_new
>  	if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
>
>
> Changelog entry:
>
>     libstdc++-v3/ChangeLog:
>
>             * include/bits/atomic_base.h: Fix -Wunused-variable
>             in system headers.
>             * include/ext/new_allocator.h: Fix -Wunused-parameter
>             in system headers.
>
>
> Test suite confirmation:
> All tests pass. Tested on both Manjaro and some Ubuntu 18.04 with gcc10
> and gcc8 respectively.
>
> On Mon, 24 Aug 2020 at 13:59, Jonathan Wakely <jwakely@redhat.com> wrote:
>
>> On 24/08/20 13:26 +0200, Krystian Kuźniarek via Libstdc++ wrote:
>> >Hi,
>> >
>> >First of all, sorry, I must have sent it as quoted-printable so spaces
>> and
>> >tabs are preserved.
>> >
>> >A description of the problem/bug and how your patch addresses it:
>> >I've got a small patch for -Wunused-variable and -Wunused-parameter in
>> >system headers. These are needed either for:
>> >1) __glibcxx_assert() that quickly goes away during an early compilation
>> >step leaving the warning
>> >2) code that conditionally is removed by preprocessor leaving the warning
>> >
>> >Testcases:
>> >N/A, it's only a warning.
>> >
>> >ChangeLog:
>> >Sorry, contrib/mklog.py didn't quite work for me.
>> >For some reason after instruction in line 129: "diff = PatchSet(data)" my
>> >"diff" variable is always empty.
>> >
>> >Bootstrapping and testing:
>> >Tested that manually by recompling GCC, unfolding all headers with
>> >`#include <stdc++.h>` and compiling what's been included by it.
>> >
>> >The patch itself:
>> >
>> >diff --git a/libstdc++-v3/include/bits/atomic_base.h
>> >b/libstdc++-v3/include/bits/atomic_base.h
>> >index 015acef83c4..1fbb2d78d28 100644
>> >--- a/libstdc++-v3/include/bits/atomic_base.h
>> >+++ b/libstdc++-v3/include/bits/atomic_base.h
>> >@@ -231,7 +231,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>> >     _GLIBCXX_ALWAYS_INLINE void
>> >     clear(memory_order __m = memory_order_seq_cst) noexcept
>> >     {
>> >-      memory_order __b = __m & __memory_order_mask;
>> >+      memory_order __b __attribute__ ((__unused__)) =
>>
>> Thanks for the patch.
>>
>> Please put the line break before the '=' character i.e.
>>
>>        memory_order __b __attribute__ ((__unused__))
>>          = __m & __memory_order_mask;
>>
>> Other than that, the patch looks ok, and simple enough to not need a
>> copyright assignment for GCC.
>>
>> A changelog entry and confirmation the testsuite still runs would be
>> preferred though.
>>
>>