Re: [PATCH v2] disas: converts malloc to g_new0

[Markus Armbruster <armbru@redhat.com>]

"Christian S. Lima" <christianslima@proton.me> writes:

> Following the qemu coding style change from malloc to g_new0, the
> advantages are that g_new0 catch multiplication overflowing size_t,
> allows for better detection of type errors because it returns the type
> itself and initialize memory with zeros to detect if something go wrong.

In general, just-in-case zero-initialization won't detect anything, it
just converts unpredictable bad behavior to predictable bad behavior.

In this case, it does exactly nothing, as we'll see below.

>
> Signed-off-by: Christian S. Lima <christianslima@proton.me>
> ---
> Changes in v2:
>     - Change from g_malloc0 to g_new0
> ---
>  disas/m68k.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/disas/m68k.c b/disas/m68k.c
> index 800b4145ac..c3571783b0 100644
> --- a/disas/m68k.c
> +++ b/disas/m68k.c
> @@ -1887,8 +1887,7 @@ print_insn_m68k (bfd_vma memaddr, disassemble_info *info)
>  
>        /* Then create a sorted table of pointers
>  	 that point into the unsorted table.  */
> -      opc_pointer[0] = malloc (sizeof (struct m68k_opcode *)
> -                               * m68k_numopcodes);
> +      opc_pointer[0] = g_new0(const struct m68k_opcode *, m68k_numopcodes);
>        opcodes[0] = opc_pointer[0];
>  
>        for (i = 1; i < 16; i++)
           {
             opc_pointer[i] = opc_pointer[i - 1] + numopcodes[i - 1];
             opcodes[i] = opc_pointer[i];
           }

This obviously overwrites every single bit in opc_pointer[], i.e. the
switch from allocating uninitialized to zero-initialzed memory is a
complete waste.  I'd use g_new().  Up to the maintainer.

Either way,
Reviewed-by: Markus Armbruster <armbru@redhat.com>