Additional information.
From: Masato Asou <[email protected]>
Subject: Use `if (retval == -1)' instead of 'if (retval < 0)'
Date: Wed, 14 Aug 2019 13:42:13 +0900 (JST)
> Hi tech,
>
> Use `if (retval == -1)' instead of 'if (retval < 0)' when check the
> return value of system call.
>
> How about it?
>
> RCS file: /cvs/src/lib/libedit/readline.c,v
> retrieving revision 1.28
> diff -u -p -u -r1.28 readline.c
> --- readline.c 28 Jun 2019 13:32:42 -0000 1.28
> +++ readline.c 14 Aug 2019 04:38:55 -0000
> @@ -2112,7 +2112,7 @@ _rl_event_read_char(EditLine *el, wchar_
> return -1;
> #endif
>
> - if (num_read < 0 && errno == EAGAIN)
> + if (num_read == -1 && errno == EAGAIN)
> continue;
> if (num_read == 0)
> continue;
> --
> ASOU Masato
The valiable num_read has a return value of READ(2) system call as follows:
2090 while (rl_event_hook) {
2091
2092 (*rl_event_hook)();
2093
2094 #if defined(FIONREAD)
2095 if (ioctl(el->el_infd, FIONREAD, &n) == -1)
2096 return -1;
2097 if (n)
2098 num_read = read(el->el_infd, &ch, 1);
2099 else
2100 num_read = 0;
2101 #elif defined(F_SETFL) && defined(O_NDELAY)
2102 if ((n = fcntl(el->el_infd, F_GETFL)) == -1)
2103 return -1;
2104 if (fcntl(el->el_infd, F_SETFL, n|O_NDELAY) ==
-1)
2105 return -1;
2106 num_read = read(el->el_infd, &ch, 1);
2107 if (fcntl(el->el_infd, F_SETFL, n))
2108 return -1;
2109 #else
2110 /* not non-blocking, but what you gonna do? */
2111 num_read = read(el->el_infd, &ch, 1);
2112 return -1;
2113 #endif
2114
2115 if (num_read < 0 && errno == EAGAIN)
2116 continue;
2117 if (num_read == 0)
2118 continue;
2119 break;
2120 }
--
ASOU Masato
