[Bug build/29373] New: Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[Bug build/29373] New: Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[euloanty at live dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

            Bug ID: 29373
           Summary: Canadian Compilation Failed!
                    gdbsupport/packed.h:41:40: error: static assertion
                    failed for x86_64-w64-mingw32 host.
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: build
          Assignee: unassigned at sourceware dot org
          Reporter: euloanty at live dot com
  Target Milestone: ---

Created attachment 14214
  --> https://sourceware.org/bugzilla/attachment.cgi?id=14214&action=edit
build failure

gdbsupport's static_assert breaks x86_64-w64-mingw32 host.

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[euloanty at live dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

cqwrteur <euloanty at live dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P2                          |P1
                 CC|                            |euloanty at live dot com
              Build|                            |x86_64-linux-gnu
               Host|                            |x86_64-w64-mingw32
             Target|                            |i586-msdosdjgpp

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[euloanty at live dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #1 from cqwrteur <euloanty at live dot com> ---
Created attachment 14215
  --> https://sourceware.org/bugzilla/attachment.cgi?id=14215&action=edit
config file

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |palves at sourceware dot org,
                   |                            |tromey at sourceware dot org,
                   |                            |vries at gcc dot gnu.org

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-07-18

--- Comment #2 from Tom Tromey <tromey at sourceware dot org> ---
Pedro, Tom -- FWIW we encountered this internally @ AdaCore as well.
The sizeof assert fails, I guess (I didn't look) due to a difference
in the Windows ABI.  It seems to me that just removing the assert
is probably fine.

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
I wonder if this is indeed an abi issue, or if it's basically complaining that
it's missing the alternative implementation of the the packed template, not
relying on a packed attribute implementation, that Pedro initially proposed.

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

Pedro Alves <pedro at palves dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pedro at palves dot net

--- Comment #4 from Pedro Alves <pedro at palves dot net> ---
I can reproduce this here, cross building with mingw on Fedora.

This is indeed an ABI issue -- mingw defaults to "-mms-bitfields", which
affects how bitfields are laid out.  Luckily, there's an attribute to switch
ABI on a per struct basis.  See:

  https://gcc.gnu.org/onlinedocs/gcc/x86-Variable-Attributes.html

This fixes the build for me:

diff --git c/gdbsupport/packed.h w/gdbsupport/packed.h
index 3468cf44207..a3389afdfb7 100644
--- c/gdbsupport/packed.h
+++ w/gdbsupport/packed.h
@@ -20,6 +20,12 @@

 #include "traits.h"

+#ifdef __MINGW32__
+# define ATTRIBUTE_GCC_STRUCT  __attribute__((gcc_struct))
+#else
+# define ATTRIBUTE_GCC_STRUCT
+#endif
+
 /* Each instantiation and full specialization of the packed template
    defines a type that behaves like a given scalar type, but that has
    byte alignment, and, may optionally have a smaller size than the
@@ -58,7 +64,7 @@ struct packed

 private:
   T m_val : (Bytes * HOST_CHAR_BIT) ATTRIBUTE_PACKED;
-};
+} ATTRIBUTE_GCC_STRUCT;

 /* Add some comparisons between std::atomic<packed<T>> and T.  We need
    this because the regular comparisons would require two implicit

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[euloanty at live dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #5 from cqwrteur <euloanty at live dot com> ---
(In reply to Pedro Alves from comment #4)
> I can reproduce this here, cross building with mingw on Fedora.
> 
> This is indeed an ABI issue -- mingw defaults to "-mms-bitfields", which
> affects how bitfields are laid out.  Luckily, there's an attribute to switch
> ABI on a per struct basis.  See:
> 
>   https://gcc.gnu.org/onlinedocs/gcc/x86-Variable-Attributes.html
> 
> This fixes the build for me:
> 
> diff --git c/gdbsupport/packed.h w/gdbsupport/packed.h
> index 3468cf44207..a3389afdfb7 100644
> --- c/gdbsupport/packed.h
> +++ w/gdbsupport/packed.h
> @@ -20,6 +20,12 @@
>  
>  #include "traits.h"
>  
> +#ifdef __MINGW32__
> +# define ATTRIBUTE_GCC_STRUCT  __attribute__((gcc_struct))
> +#else
> +# define ATTRIBUTE_GCC_STRUCT
> +#endif
> +
>  /* Each instantiation and full specialization of the packed template
>     defines a type that behaves like a given scalar type, but that has
>     byte alignment, and, may optionally have a smaller size than the
> @@ -58,7 +64,7 @@ struct packed
>  
>  private:
>    T m_val : (Bytes * HOST_CHAR_BIT) ATTRIBUTE_PACKED;
> -};
> +} ATTRIBUTE_GCC_STRUCT;
>  
>  /* Add some comparisons between std::atomic<packed<T>> and T.  We need
>     this because the regular comparisons would require two implicit

Also cygwin and other pe targets.

you probably need 


#if __has_cpp_attribute(__gnu__::__gcc_struct__)
#define ATTRIBUTE_GCC_STRUCT [[__gnu__::__gcc_struct__]]
#endif

something like that to detect the feature

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #6 from Pedro Alves <pedro at palves dot net> ---
> Also cygwin and other pe targets.

Does Cygwin default to "-mms-bitfields" too?

What other PE hosts are there?  (It's hosts that matter here, not targets.)

> #if __has_cpp_attribute(__gnu__::__gcc_struct__)
> #define ATTRIBUTE_GCC_STRUCT [[__gnu__::__gcc_struct__]]
> #endif

An issue with that is that __has_attribute and __has_cpp_attribute were added
in GCC 5, while supposedly the minimum supported GCC version for building GDB
is GCC 4.8.  I have no idea whether anyone out there would still build GDB for
Windows using that version of GCC, though.  Explicitly checking mingw/cygwin
would work there too, as __gcc_struct__ was already supported back then.

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #7 from Pedro Alves <pedro at palves dot net> ---
Googling around, I found that Clang for Windows does not support the gcc_struct
attribute.  E.g., here:

 https://code.videolan.org/videolan/libdvdread/-/issues/19

with that in mind, I added back (or rather, reimplemented), the fallback
implementation using byte arrays, and make _WIN32 + clang use it.  To make sure
it all behaves as intended, I wrote some units tests.

I don't think I'll have to post this to the list today, so I pushed it to the
users/palves/packed branch on sourceware.

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #8 from Pedro Alves <pedro at palves dot net> ---
... I'll have TIME to post this ...

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #9 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Pedro Alves from comment #7)
> ... I pushed it to
> the users/palves/packed branch on sourceware.

I've build the patch with gcc 4.8.5, and ran into:
...
In file included from gdb/unittests/packed-selftests.c:22:0:
gdbsupport/packed.h:120:27: error: ‘atomic’ in namespace ‘std’ does not name a
type
   bool operator OP (const std::atomic<packed<T, Bytes>> &lhs,  \
                           ^
gdbsupport/packed.h:152:1: note: in expansion of macro ‘PACKED_ATOMIC_OP’
 PACKED_ATOMIC_OP (==)
 ^
...

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #10 from Pedro Alves <pedro at palves dot net> ---
Thanks, I'll try to reproduce it.  It's probably just missing #include
<atomic>.

BTW, I tried building unittests/packed-selftests.c with "clang -target
x86_64-pc-windows-gnu", and turns out that even though clang doesn't support
gcc_struct, it actually doesn't need it, the static asserts pass without it. 
So I'm dropping the array based implementation, again...

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #11 from Pedro Alves <pedro at palves dot net> ---
LOL, neverending story.  Clang 10 doesn't need the alternative implementation,
but clang 14 does.  Maybe Clang didn't implement MS bitfields properly in
version 10 yet.

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #12 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Pedro Alves from comment #10)
> Thanks, I'll try to reproduce it.  It's probably just missing #include
> <atomic>.
> 

Ack, managed to build with gcc 4.8.5 and:
...
diff --git a/gdbsupport/packed.h b/gdbsupport/packed.h
index d65e0bc33f0..097bd493fa4 100644
--- a/gdbsupport/packed.h
+++ b/gdbsupport/packed.h
@@ -18,6 +18,7 @@
 #ifndef PACKED_H
 #define PACKED_H

+#include <atomic>
 #include "traits.h"

 /* Each instantiation and full specialization of the packed template
...

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #13 from Pedro Alves <pedro at palves dot net> ---
Thanks.

Posted here now:

  [PATCH 0/3] struct packed and Windows ports (PR build/29373)
  https://sourceware.org/pipermail/gdb-patches/2022-July/190957.html

I've confirmed this builds with gcc version 4.8.5, too.

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

--- Comment #14 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pedro Alves <palves@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e249e6b8012ea0a14e5768d31becd7b4caff8e77

commit e249e6b8012ea0a14e5768d31becd7b4caff8e77
Author: Pedro Alves <pedro@palves.net>
Date:   Tue Jul 19 00:26:33 2022 +0100

    struct packed: Unit tests and more operators

    For PR gdb/29373, I wrote an alternative implementation of struct
    packed that uses a gdb_byte array for internal representation, needed
    for mingw+clang.  While adding that, I wrote some unit tests to make
    sure both implementations behave the same.  While at it, I implemented
    all relational operators.  This commit adds said unit tests and
    relational operators.  The alternative gdb_byte array implementation
    will come next.

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29373

    Change-Id: I023315ee03622c59c397bf4affc0b68179c32374

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[Bug build/29373] Canadian Compilation Failed! gdbsupport/packed.h:41:40: error: static assertion failed for x86_64-w64-mingw32 host.

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=29373

Pedro Alves <pedro at palves dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |13.1
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED

--- Comment #15 from Pedro Alves <pedro at palves dot net> ---
Should be fixed now.

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