Re: [PATCH 1/2] core: use env variable instead of config var to turn on logging pack access

[Junio C Hamano <gitster@pobox.com>]

Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:

> diff --git a/sha1_file.c b/sha1_file.c
> index 67e815b..7b47bdc 100644
> --- a/sha1_file.c
> +++ b/sha1_file.c
> @@ -36,6 +36,8 @@ static inline uintmax_t sz_fmt(size_t s) { return s; }
>  
>  const unsigned char null_sha1[20];
>  
> +static const char *log_pack_access = "";
> +
>  /*
>   * This is meant to hold a *small* number of objects that you would
>   * want read_sha1_file() to be able to return, but yet you do not want
> @@ -1956,6 +1958,14 @@ static void write_pack_access_log(struct packed_git *p, off_t obj_offset)
>  {
>  	static FILE *log_file;
>  
> +	if (!*log_pack_access) {
> +		log_pack_access = getenv("GIT_TRACE_PACK_ACCESS");
> +		if (!*log_pack_access)
> +			log_pack_access = NULL;
> +		if (!log_pack_access)
> +			return;
> +	}

Have you ever tested this?

Once log_pack_access goes to NULL (e.g. when it sees the empty
string it was initialized to), this new test will happily
dereference NULL.