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From: "pedro at palves dot net" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug build/29373] Canadian Compilation Failed!
 gdbsupport/packed.h:41:40: error: static assertion failed for
 x86_64-w64-mingw32 host.
Date: Mon, 18 Jul 2022 23:34:02 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D29373

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

--=20
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