Re: [PATCH] gdb: add constructor to gdb_user_regs

[Tom de Vries <tdevries@suse.de>]

On 8/6/22 07:14, Enze Li via Gdb-patches wrote:
> When building gdb with clang 14 and -std=gnu++11, I ran into:
> 
>    CXX    user-regs.o
> user-regs.c:83:29: error: no matching constructor for initialization of 'struct gdb_user_regs'
> static struct gdb_user_regs builtin_user_regs = {
>                              ^                   ~
> user-regs.c:58:8: note: candidate constructor (the implicit copy constructor) not viable: requires 1 argument, but 2 were provided
> struct gdb_user_regs
>         ^
> user-regs.c:58:8: note: candidate constructor (the implicit move constructor) not viable: requires 1 argument, but 2 were provided
> user-regs.c:58:8: note: candidate constructor (the implicit default constructor) not viable: requires 0 arguments, but 2 were provided
> 1 error generated.
> 
> The fundamental reason is that C++11 does not support this approach.
> This patch adds a constructor to gdb_user_regs to avoid the build
> failure.
> 

Hi,

I ran into a similar problem with gcc 4.8 (I noticed a build failure 
with centos @ builder.sourceware.org) and fixed it here ( 
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=411c7e044fa99089d3030f2c61525c4d415f7b45 
).

My apologies that I didn't notice your patch.

Anyway, I hope that this fixes the problem for you as well.  I've 
managed to do a build using clang-13.0.0 (with --disable-werror) up to 
the point of an AFAICT unrelated linker failure.

Thanks,
- Tom

> Tested by rebuilding on x86_64-linux with clang 14 and gcc 12, with and
> without -std=gnu++11.
> ---
>   gdb/user-regs.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/gdb/user-regs.c b/gdb/user-regs.c
> index 4bc4685387f..a2012b84534 100644
> --- a/gdb/user-regs.c
> +++ b/gdb/user-regs.c
> @@ -57,8 +57,16 @@ struct user_reg
>   
>   struct gdb_user_regs
>   {
> -  struct user_reg *first = nullptr;
> -  struct user_reg **last = nullptr;
> +  gdb_user_regs (struct user_reg *mfirst, struct user_reg **mlast)
> +    : first (mfirst),
> +      last (mlast)
> +  {
> +  }
> +
> +  gdb_user_regs () = default;
> +
> +  struct user_reg *first;
> +  struct user_reg **last;
>   };
>   
>   static void