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* [PATCH] libstdc++: Fix filesystem::path constraints for volatile [PR 100630]
@ 2021-05-17 14:02 Jonathan Wakely
  2021-05-17 14:25 ` Jonathan Wakely
  0 siblings, 1 reply; 3+ messages in thread
From: Jonathan Wakely @ 2021-05-17 14:02 UTC (permalink / raw)
  To: libstdc++, gcc-patches

[-- Attachment #1: Type: text/plain, Size: 1067 bytes --]

The constraint check for filesystem::path construction uses
decltype(__is_path_src(declval<Source>())) which mean it considers
conversion from an rvalue.  When Source is a volatile-qualified type
it cannot use is_path_src(const Unknown&) because a const lvalue
reference can only bind to a non-volatile rvalue.

Since the relevant path members all have a const Source& parameter,
the constraint should be defined in terms of declval<const Source&>(),
not declval<Source>(). This avoids the problem of volatile-qualified
rvalues, because we no longer use an rvalue at all.

libstdc++-v3/ChangeLog:

	PR libstdc++/100630
	* include/bits/fs_path.h (__is_constructible_from): Test
	construction from a const lvalue, not an rvalue.
	* include/experimental/bits/fs_path.h (__is_constructible_from):
	Likewise.
	* testsuite/27_io/filesystem/path/construct/100630.cc: New test.
	* testsuite/experimental/filesystem/path/construct/100630.cc:
	New test.

Tested x86_64-linux, pushed to gcc-10 (this isn't needed for gcc-11 or
trunk, but I also plan to backport it to gcc-9).



[-- Attachment #2: patch.txt --]
[-- Type: text/plain, Size: 3468 bytes --]

commit 4cd69a5a0dd31bc6fdef1bbabc8d6d1416014ea1
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon May 17 11:54:06 2021

    libstdc++: Fix filesystem::path constraints for volatile [PR 100630]
    
    The constraint check for filesystem::path construction uses
    decltype(__is_path_src(declval<Source>())) which mean it considers
    conversion from an rvalue.  When Source is a volatile-qualified type
    it cannot use is_path_src(const Unknown&) because a const lvalue
    reference can only bind to a non-volatile rvalue.
    
    Since the relevant path members all have a const Source& parameter,
    the constraint should be defined in terms of declval<const Source&>(),
    not declval<Source>(). This avoids the problem of volatile-qualified
    rvalues, because we no longer use an rvalue at all.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/100630
            * include/bits/fs_path.h (__is_constructible_from): Test
            construction from a const lvalue, not an rvalue.
            * include/experimental/bits/fs_path.h (__is_constructible_from):
            Likewise.
            * testsuite/27_io/filesystem/path/construct/100630.cc: New test.
            * testsuite/experimental/filesystem/path/construct/100630.cc:
            New test.

diff --git a/libstdc++-v3/include/bits/fs_path.h b/libstdc++-v3/include/bits/fs_path.h
index 3d341916db5..6e0a85417cc 100644
--- a/libstdc++-v3/include/bits/fs_path.h
+++ b/libstdc++-v3/include/bits/fs_path.h
@@ -116,7 +116,7 @@ namespace __detail
 
   template<typename _Source>
     struct __constructible_from<_Source, void>
-    : decltype(__is_path_src(std::declval<_Source>(), 0))
+    : decltype(__is_path_src(std::declval<const _Source&>(), 0))
     { };
 
   template<typename _Tp1, typename _Tp2 = void>
diff --git a/libstdc++-v3/include/experimental/bits/fs_path.h b/libstdc++-v3/include/experimental/bits/fs_path.h
index c5fc3beed1f..0a8f4eee0a1 100644
--- a/libstdc++-v3/include/experimental/bits/fs_path.h
+++ b/libstdc++-v3/include/experimental/bits/fs_path.h
@@ -124,7 +124,7 @@ namespace __detail
 
   template<typename _Source>
     struct __constructible_from<_Source, void>
-    : decltype(__is_path_src(std::declval<_Source>(), 0))
+    : decltype(__is_path_src(std::declval<const _Source&>(), 0))
     { };
 
   template<typename _Tp1, typename _Tp2 = void,
diff --git a/libstdc++-v3/testsuite/27_io/filesystem/path/construct/100630.cc b/libstdc++-v3/testsuite/27_io/filesystem/path/construct/100630.cc
new file mode 100644
index 00000000000..eb8473e600e
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/filesystem/path/construct/100630.cc
@@ -0,0 +1,14 @@
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+#include <filesystem>
+
+void f(bool) { }
+void f(const std::filesystem::path&) { }
+
+void
+test_100630()
+{
+  volatile bool b = true;
+  f(b);
+}
diff --git a/libstdc++-v3/testsuite/experimental/filesystem/path/construct/100630.cc b/libstdc++-v3/testsuite/experimental/filesystem/path/construct/100630.cc
new file mode 100644
index 00000000000..b2428ff74cf
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/filesystem/path/construct/100630.cc
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++11 } }
+// { dg-require-filesystem-ts "" }
+
+#include <experimental/filesystem>
+
+void f(bool) { }
+void f(const std::experimental::filesystem::path&) { }
+
+void
+test_100630()
+{
+  volatile bool b = true;
+  f(b);
+}

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] libstdc++: Fix filesystem::path constraints for volatile [PR 100630]
  2021-05-17 14:02 [PATCH] libstdc++: Fix filesystem::path constraints for volatile [PR 100630] Jonathan Wakely
@ 2021-05-17 14:25 ` Jonathan Wakely
  2021-05-17 17:14   ` Jonathan Wakely
  0 siblings, 1 reply; 3+ messages in thread
From: Jonathan Wakely @ 2021-05-17 14:25 UTC (permalink / raw)
  To: libstdc++, gcc-patches

On 17/05/21 15:02 +0100, Jonathan Wakely wrote:
>The constraint check for filesystem::path construction uses
>decltype(__is_path_src(declval<Source>())) which mean it considers
>conversion from an rvalue.  When Source is a volatile-qualified type
>it cannot use is_path_src(const Unknown&) because a const lvalue
>reference can only bind to a non-volatile rvalue.
>
>Since the relevant path members all have a const Source& parameter,
>the constraint should be defined in terms of declval<const Source&>(),
>not declval<Source>(). This avoids the problem of volatile-qualified
>rvalues, because we no longer use an rvalue at all.
>
>libstdc++-v3/ChangeLog:
>
>	PR libstdc++/100630
>	* include/bits/fs_path.h (__is_constructible_from): Test
>	construction from a const lvalue, not an rvalue.
>	* include/experimental/bits/fs_path.h (__is_constructible_from):
>	Likewise.
>	* testsuite/27_io/filesystem/path/construct/100630.cc: New test.
>	* testsuite/experimental/filesystem/path/construct/100630.cc:
>	New test.
>
>Tested x86_64-linux, pushed to gcc-10 (this isn't needed for gcc-11 or
>trunk, but I also plan to backport it to gcc-9).

Oh actually this is needed for experimental::filesystem::path on trun
kand gcc-11 (as I found when I added to the new tests to trunk) so
I'll fix it there too.


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] libstdc++: Fix filesystem::path constraints for volatile [PR 100630]
  2021-05-17 14:25 ` Jonathan Wakely
@ 2021-05-17 17:14   ` Jonathan Wakely
  0 siblings, 0 replies; 3+ messages in thread
From: Jonathan Wakely @ 2021-05-17 17:14 UTC (permalink / raw)
  To: libstdc++, gcc-patches

[-- Attachment #1: Type: text/plain, Size: 1416 bytes --]

On 17/05/21 15:25 +0100, Jonathan Wakely wrote:
>On 17/05/21 15:02 +0100, Jonathan Wakely wrote:
>>The constraint check for filesystem::path construction uses
>>decltype(__is_path_src(declval<Source>())) which mean it considers
>>conversion from an rvalue.  When Source is a volatile-qualified type
>>it cannot use is_path_src(const Unknown&) because a const lvalue
>>reference can only bind to a non-volatile rvalue.
>>
>>Since the relevant path members all have a const Source& parameter,
>>the constraint should be defined in terms of declval<const Source&>(),
>>not declval<Source>(). This avoids the problem of volatile-qualified
>>rvalues, because we no longer use an rvalue at all.
>>
>>libstdc++-v3/ChangeLog:
>>
>>	PR libstdc++/100630
>>	* include/bits/fs_path.h (__is_constructible_from): Test
>>	construction from a const lvalue, not an rvalue.
>>	* include/experimental/bits/fs_path.h (__is_constructible_from):
>>	Likewise.
>>	* testsuite/27_io/filesystem/path/construct/100630.cc: New test.
>>	* testsuite/experimental/filesystem/path/construct/100630.cc:
>>	New test.
>>
>>Tested x86_64-linux, pushed to gcc-10 (this isn't needed for gcc-11 or
>>trunk, but I also plan to backport it to gcc-9).
>
>Oh actually this is needed for experimental::filesystem::path on trun
>kand gcc-11 (as I found when I added to the new tests to trunk) so
>I'll fix it there too.

Here's the patch for trunk and gcc-11.


[-- Attachment #2: patch.txt --]
[-- Type: text/x-patch, Size: 2868 bytes --]

commit 45aa7a447652e8541cc381d7ab128544f81ed857
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon May 17 11:54:06 2021

    libstdc++: Fix filesystem::path constraints for volatile [PR 100630]
    
    The constraint check for filesystem::path construction uses
    decltype(__is_path_src(declval<Source>())) which mean it considers
    conversion from an rvalue.  When Source is a volatile-qualified type
    it cannot use is_path_src(const Unknown&) because a const lvalue
    reference can only bind to a non-volatile rvalue.
    
    Since the relevant path members all have a const Source& parameter,
    the constraint should be defined in terms of declval<const Source&>(),
    not declval<Source>(). This avoids the problem of volatile-qualified
    rvalues, because we no longer use an rvalue at all.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/100630
            * include/experimental/bits/fs_path.h (__is_constructible_from):
            Test construction from a const lvalue, not an rvalue.
            * testsuite/27_io/filesystem/path/construct/100630.cc: New test.
            * testsuite/experimental/filesystem/path/construct/100630.cc:
            New test.

diff --git a/libstdc++-v3/include/experimental/bits/fs_path.h b/libstdc++-v3/include/experimental/bits/fs_path.h
index 2df2bba3dcd..1ecf2f3a7bd 100644
--- a/libstdc++-v3/include/experimental/bits/fs_path.h
+++ b/libstdc++-v3/include/experimental/bits/fs_path.h
@@ -124,7 +124,7 @@ namespace __detail
 
   template<typename _Source>
     struct __constructible_from<_Source, void>
-    : decltype(__is_path_src(std::declval<_Source>(), 0))
+    : decltype(__is_path_src(std::declval<const _Source&>(), 0))
     { };
 
   template<typename _Tp1, typename _Tp2 = void,
diff --git a/libstdc++-v3/testsuite/27_io/filesystem/path/construct/100630.cc b/libstdc++-v3/testsuite/27_io/filesystem/path/construct/100630.cc
new file mode 100644
index 00000000000..eb8473e600e
--- /dev/null
+++ b/libstdc++-v3/testsuite/27_io/filesystem/path/construct/100630.cc
@@ -0,0 +1,14 @@
+// { dg-options "-std=gnu++17" }
+// { dg-do compile { target c++17 } }
+
+#include <filesystem>
+
+void f(bool) { }
+void f(const std::filesystem::path&) { }
+
+void
+test_100630()
+{
+  volatile bool b = true;
+  f(b);
+}
diff --git a/libstdc++-v3/testsuite/experimental/filesystem/path/construct/100630.cc b/libstdc++-v3/testsuite/experimental/filesystem/path/construct/100630.cc
new file mode 100644
index 00000000000..b2428ff74cf
--- /dev/null
+++ b/libstdc++-v3/testsuite/experimental/filesystem/path/construct/100630.cc
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++11 } }
+// { dg-require-filesystem-ts "" }
+
+#include <experimental/filesystem>
+
+void f(bool) { }
+void f(const std::experimental::filesystem::path&) { }
+
+void
+test_100630()
+{
+  volatile bool b = true;
+  f(b);
+}

^ permalink raw reply	[flat|nested] 3+ messages in thread

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2021-05-17 17:14   ` Jonathan Wakely

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