libbb: introduce and use nonblock_safe_read(). Yay!

Our shells are immune from this nasty O_NONBLOCK now!

function                                             old     new   delta
nonblock_safe_read                                     -      78     +78
file_get                                             276     295     +19
generateMTFValues                                    428     435      +7
read_line_input                                     1776    1772      -4
preadbuffer                                          543     450     -93
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/2 up/down: 104/-97)             Total: 7 bytes
   text    data     bss     dec     hex filename
 615190     715   23924  639829   9c355 busybox_old
 615168     715   23924  639807   9c33f busybox_unstripped

3 files changed, 16 insertions, 12 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 65f94f682..debe8ecdd 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -5428,7 +5428,7 @@ expbackq(union node *cmd, int quoted, int quotes)
  read:
                 if (in.fd < 0)
                         break;
-                i = safe_read(in.fd, buf, sizeof(buf));
+                i = nonblock_safe_read(in.fd, buf, sizeof(buf));
                 TRACE(("expbackq: read returns %d\n", i));
                 if (i <= 0)
                         break;
@@ -8678,7 +8678,7 @@ preadfd(void)
  retry:
 #if ENABLE_FEATURE_EDITING
         if (!iflag || parsefile->fd)
-                nr = safe_read(parsefile->fd, buf, BUFSIZ - 1);
+                nr = nonblock_safe_read(parsefile->fd, buf, BUFSIZ - 1);
         else {
 #if ENABLE_FEATURE_TAB_COMPLETION
                 line_input_state->path_lookup = pathval();
@@ -8700,9 +8700,11 @@ preadfd(void)
                 }
         }
 #else
-        nr = safe_read(parsefile->fd, buf, BUFSIZ - 1);
+        nr = nonblock_safe_read(parsefile->fd, buf, BUFSIZ - 1);
 #endif
 
+#if 0
+/* nonblock_safe_read() handles this problem */
         if (nr < 0) {
                 if (parsefile->fd == 0 && errno == EWOULDBLOCK) {
                         int flags = fcntl(0, F_GETFL);
@@ -8715,6 +8717,7 @@ preadfd(void)
                         }
                 }
         }
+#endif
         return nr;
 }
 
@@ -11801,7 +11804,7 @@ readcmd(int argc, char **argv)
         backslash = 0;
         STARTSTACKSTR(p);
         do {
-                if (read(0, &c, 1) != 1) {
+                if (nonblock_safe_read(0, &c, 1) != 1) {
                         status = 1;
                         break;
                 }
diff --git a/shell/hush.c b/shell/hush.c
index 4d4843173..820fd888d 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -1273,10 +1273,10 @@ static void get_user_input(struct in_str *i)
         prompt_str = setup_prompt_string(i->promptmode);
 #if ENABLE_FEATURE_EDITING
         /* Enable command line editing only while a command line
-         * is actually being read; otherwise, we'll end up bequeathing
-         * atexit() handlers and other unwanted stuff to our
-         * child processes (rob@sysgo.de) */
-        r = read_line_input(prompt_str, user_input_buf, BUFSIZ-1, line_input_state);
+         * is actually being read */
+        do {
+                r = read_line_input(prompt_str, user_input_buf, BUFSIZ-1, line_input_state);
+        } while (r == 0); /* repeat if Ctrl-C */
         i->eof_flag = (r < 0);
         if (i->eof_flag) { /* EOF/error detected */
                 user_input_buf[0] = EOF; /* yes, it will be truncated, it's ok */
diff --git a/shell/msh.c b/shell/msh.c
index fd287f16e..917b08a1e 100644
--- a/shell/msh.c
+++ b/shell/msh.c
@@ -42,6 +42,7 @@
 # define xmalloc(size) malloc(size)
 # define msh_main(argc,argv) main(argc,argv)
 # define safe_read(fd,buf,count) read(fd,buf,count)
+# define nonblock_safe_read(fd,buf,count) read(fd,buf,count)
 # define NOT_LONE_DASH(s) ((s)[0] != '-' || (s)[1])
 # define LONE_CHAR(s,c) ((s)[0] == (c) && !(s)[1])
 # define ATTRIBUTE_NORETURN __attribute__ ((__noreturn__))
@@ -3376,7 +3377,7 @@ static int doread(struct op *t)
         }
         for (wp = t->words + 1; *wp; wp++) {
                 for (cp = global_env.linep; !nl && cp < elinep - 1; cp++) {
-                        nb = read(0, cp, sizeof(*cp));
+                        nb = nonblock_safe_read(0, cp, sizeof(*cp));
                         if (nb != sizeof(*cp))
                                 break;
                         nl = (*cp == '\n');
@@ -4799,7 +4800,7 @@ static int filechar(struct ioarg *ap)
                         if (i)
                                 lseek(ap->afile, ap->afpos, SEEK_SET);
 
-                        i = safe_read(ap->afile, bp->buf, sizeof(bp->buf));
+                        i = nonblock_safe_read(ap->afile, bp->buf, sizeof(bp->buf));
                         if (i <= 0) {
                                 closef(ap->afile);
                                 return 0;
@@ -4830,7 +4831,7 @@ static int filechar(struct ioarg *ap)
                 return c;
         }
 #endif
-        i = safe_read(ap->afile, &c, sizeof(c));
+        i = nonblock_safe_read(ap->afile, &c, sizeof(c));
         return i == sizeof(c) ? (c & 0x7f) : (closef(ap->afile), 0);
 }
 
@@ -4841,7 +4842,7 @@ static int herechar(struct ioarg *ap)
 {
         char c;
 
-        if (read(ap->afile, &c, sizeof(c)) != sizeof(c)) {
+        if (nonblock_safe_read(ap->afile, &c, sizeof(c)) != sizeof(c)) {
                 close(ap->afile);
                 c = '\0';
         }