[ovs-dev] [PATCH] fatal-signal: Remove snprintf.

[Ben Pfaff]

On Wed, Mar 25, 2020 at 07:34:13AM -0700, William Tu wrote:
> Function snprintf is not async-signal-safe.  Replace it with
> our own implementation.  Example ovs-vswitchd.log output:
>   2020-03-25T01:08:19.673Z|00050|memory|INFO|handlers:2 ports:3
>   SIGSEGV detected, backtrace:
>   0x4872d9         <fatal_signal_handler+0x49>
>   0x7f4e2ab974b0   <killpg+0x40>
>   0x7f4e2ac5d74d   <__poll+0x2d>
>   0x531098         <time_poll+0x108>
>   0x51aefc         <poll_block+0x8c>
>   0x445ca9         <udpif_revalidator+0x289>
>   0x5056fd         <ovsthread_wrapper+0x7d>
>   0x7f4e2b65f6ba   <start_thread+0xca>
>   0x7f4e2ac6941d   <clone+0x6d>
>   0x0              <+0x0>
> 
> Tested-at: https://travis-ci.org/github/williamtu/ovs-travis/builds/666596271
> Signed-off-by: William Tu <u9012063 at gmail.com>

I didn't test this, but I assume you did.

The traditional way to get a hex digit is to write "0123456789abcdef"[x],
although your way is fine too.

If the function name is long, this will overflow the line buffer.

There's no reason to write "line =" in each of these, since strcat()
just returns its first argument.

> +            line = strcat(line, "0x");
> +            line = strcat(line, ip_str);
> +            line = strcat(line, "<");
> +            line = strcat(line, unw_bt[i].func);
> +            line = strcat(line, "+0x");
> +            line = strcat(line, offset_str);
> +            line = strcat(line, ">\n");