[binutils-gdb] nat/amd64-linux-siginfo.c: Move align attribute from typedef to struct

[Pedro Alves]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d8ca8e9facb184d67ce1aca9196ed8446e7e2a09

commit d8ca8e9facb184d67ce1aca9196ed8446e7e2a09
Author: Pedro Alves <pedro@palves.net>
Date:   Fri Jun 4 21:44:36 2021 +0100

    nat/amd64-linux-siginfo.c: Move align attribute from typedef to struct
    
    Compiling GDB with current git Clang (future 13) fails with (among
    other problems), this issue:
    
     $ make nat/amd64-linux-siginfo.o
       CXX    nat/amd64-linux-siginfo.o
     src/gdb/nat/amd64-linux-siginfo.c:590:35: warning: passing 4-byte aligned argument to 8-byte aligned parameter 1 of 'compat_x32_siginfo_from_siginfo' may result in an unaligned pointer access [-Walign-mismatch]
             compat_x32_siginfo_from_siginfo ((struct compat_x32_siginfo *) inf,
                                              ^
     1 warning generated.
    
    The problem is that:
    
      - The flagged code is casting to "struct compat_x32_siginfo" pointer
        directly instead of to a pointer to the compat_x32_siginfo_t
        typedef.  The called function is declared with a
        compat_x32_siginfo_t typedef pointer parameter.
    
      - Only the typedef has the __aligned__ attribute.
    
    Fix this by moving the attribute to the struct, so both struct and
    typedef have the same alignment.
    
    The next patch removes the typedefs.
    
    gdb/ChangeLog:
    yyyy-mm-dd  Pedro Alves  <pedro@palves.net>
    
            * nat/amd64-linux-siginfo.c (compat_x32_siginfo_t): Move
            __attribute__ __aligned__ from the typedef to the struct.

Diff:
---
 gdb/ChangeLog                 | 5 +++++
 gdb/nat/amd64-linux-siginfo.c | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index aa8bcb9615a..4859531e1a5 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2021-06-07  Pedro Alves  <pedro@palves.net>
+
+	* nat/amd64-linux-siginfo.c (compat_x32_siginfo_t): Move
+	__attribute__ __aligned__ from the typedef to the struct.
+
 2021-06-07  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	PR gdb/27847
diff --git a/gdb/nat/amd64-linux-siginfo.c b/gdb/nat/amd64-linux-siginfo.c
index e2d2db6e112..9ff9361487a 100644
--- a/gdb/nat/amd64-linux-siginfo.c
+++ b/gdb/nat/amd64-linux-siginfo.c
@@ -206,7 +206,7 @@ typedef struct compat_siginfo
 /* For x32, clock_t in _sigchld is 64bit aligned at 4 bytes.  */
 typedef long __attribute__ ((__aligned__ (4))) compat_x32_clock_t;
 
-typedef struct compat_x32_siginfo
+typedef struct __attribute__ ((__aligned__ (8))) compat_x32_siginfo
 {
   int si_signo;
   int si_errno;
@@ -263,7 +263,7 @@ typedef struct compat_x32_siginfo
       int _fd;
     } _sigpoll;
   } _sifields;
-} compat_x32_siginfo_t __attribute__ ((__aligned__ (8)));
+} compat_x32_siginfo_t;
 
 /* To simplify usage of siginfo fields.  */