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

Krystian Kuźniarek krystian.kuzniarek@gmail.com
Fri Aug 28 06:32:19 GMT 2020


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.
>
>


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