Re: [Tarantool-patches] [PATCH v2] refactoring: drop excess 16Kb bss buffer

[Leonid Vasiliev <lvasiliev@tarantool.org>]

On 1/23/20 11:44 AM, Sergey Kaplun wrote:
> We already have 12Kb thread-safe static buffer
> in `lib/small/small/static.h`, that can be used instead of 16Kb
> bss buffer in `src/lib/core/backtrace.cc` for backtrace payload.
> 
> Closes #4650
> ---
> 
> branch: https://github.com/tarantool/tarantool/tree/skaplun/drop-bss-buff
> issue: https://github.com/tarantool/tarantool/issues/4650
> 
>   src/lib/core/backtrace.cc | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/src/lib/core/backtrace.cc b/src/lib/core/backtrace.cc
> index 77f77b05c..c70576b53 100644
> --- a/src/lib/core/backtrace.cc
> +++ b/src/lib/core/backtrace.cc
> @@ -33,6 +33,7 @@
>   
>   #include <stdlib.h>
>   #include <stdio.h>
> +#include <assert.h>
>   
>   #include <cxxabi.h>
>   
> @@ -47,6 +48,7 @@
>   #include <libunwind.h>
>   
>   #include "small/region.h"
> +#include "small/static.h"
>   /*
>    * We use a global static buffer because it is too late to do any
>    * allocation when we are printing backtrace and fiber stack is

May be to change the comment or relocate it?

> @@ -55,8 +57,6 @@
>   
>   #define BACKTRACE_NAME_MAX 200
>   
> -static char backtrace_buf[4096 * 4];
> -
>   static __thread struct region cache_region;
>   static __thread struct mh_i64ptr_t *proc_cache = NULL;
>   
> @@ -140,8 +140,10 @@ backtrace()
>   	unw_getcontext(&unw_context);
>   	unw_cursor_t unw_cur;
>   	unw_init_local(&unw_cur, &unw_context);
> +	char *backtrace_buf = (char *)static_alloc(SMALL_STATIC_SIZE);
> +	assert(backtrace_buf);

Do a check on NULL for Release?

>   	char *p = backtrace_buf;
> -	char *end = p + sizeof(backtrace_buf) - 1;
> +	char *end = p + SMALL_STATIC_SIZE - 1;
>   	int unw_status;
>   	*p = '\0';
>   	while ((unw_status = unw_step(&unw_cur)) > 0) {
>