Re: [Qemu-devel] [PATCH v3] RISC-V: Fix riscv_isa_string memory size bug

[Philippe Mathieu-Daudé]

On 03/16/2018 06:26 PM, Michael Clark wrote:
> This version uses a constant size memory buffer sized for
> the maximum possible ISA string length. It also uses g_new
> instead of g_new0, uses more efficient logic to append
> extensions and adds manual zero termination of the string.
> 
> Cc: Palmer Dabbelt <address@hidden>
> Cc: Peter Maydell <address@hidden>
> Cc: Philippe Mathieu-Daudé <address@hidden>
> Signed-off-by: Michael Clark <address@hidden>
> ---
>  target/riscv/cpu.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 4851890..298abbd 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -391,16 +391,16 @@ static const TypeInfo riscv_cpu_type_info = {
>  char *riscv_isa_string(RISCVCPU *cpu)
>  {
>      int i;
> -    size_t maxlen = 5 + ctz32(cpu->env.misa);
> -    char *isa_string = g_new0(char, maxlen);
> -    snprintf(isa_string, maxlen, "rv%d", TARGET_LONG_BITS);
> +    const size_t maxlen = sizeof("rv128") + sizeof(riscv_exts) + 1;
> +    char *isa_str = g_new(char, maxlen);
> +    char *p = isa_str + snprintf(isa_str, maxlen, "rv%d", TARGET_LONG_BITS);
>      for (i = 0; i < sizeof(riscv_exts); i++) {
>          if (cpu->env.misa & RV(riscv_exts[i])) {
> -            isa_string[strlen(isa_string)] = riscv_exts[i] - 'A' + 'a';
> -
> +            *p++ = riscv_exts[i] - 'A' + 'a';
                                                 /* tolower() */

I prefer unobfuscated code (think newcomers and reviewers) :|

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

>          }
>      }
> -    return isa_string;
> +    *p = '\0';
> +    return isa_str;
>  }
>  
>  void riscv_cpu_list(FILE *f, fprintf_function cpu_fprintf)
>