lineedit: reduce stack usage

netstat: reduce stack usage; fix handling of NULs in unix socket filenames

static.has_inode                                       1       -      -1
do_info                                              119     116      -3
deinit_S                                              60      51      -9
unix_do_one                                          578     451    -127
parse_and_put_prompt                                 966     825    -141
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 0/4 up/down: 0/-281)           Total: -281 bytes

1 files changed, 43 insertions, 50 deletions

diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 07db6358d..1397409cc 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -91,7 +91,6 @@ struct statics {
 
         const char *cmdedit_prompt;
 #if ENABLE_FEATURE_EDITING_FANCY_PROMPT
-        char *hostname_buf;
         int num_ok_lines; /* = 1; */
 #endif
 
@@ -136,7 +135,6 @@ static struct statics *const ptr_to_statics __attribute__ ((section (".data")));
 #define command_len      (S.command_len     )
 #define command_ps       (S.command_ps      )
 #define cmdedit_prompt   (S.cmdedit_prompt  )
-#define hostname_buf     (S.hostname_buf    )
 #define num_ok_lines     (S.num_ok_lines    )
 #define user_buf         (S.user_buf        ) 
 #define home_pwd_buf     (S.home_pwd_buf    )
@@ -155,7 +153,6 @@ static struct statics *const ptr_to_statics __attribute__ ((section (".data")));
 static void deinit_S(void)
 {
 #if ENABLE_FEATURE_EDITING_FANCY_PROMPT
-        free(hostname_buf);
         /* This one is allocated only if FANCY_PROMPT is on
          * (otherwise it points to verbatim prompt (NOT malloced) */
         free((char*)cmdedit_prompt);
@@ -381,14 +378,14 @@ static void username_tab_completion(char *ud, char *with_shash_flg)
         if (with_shash_flg) {           /* "~/..." or "~user/..." */
                 char *sav_ud = ud - 1;
                 char *home = NULL;
-                char *temp;
 
                 if (*ud == '/') {       /* "~/..."     */
                         home = home_pwd_buf;
                 } else {
                         /* "~user/..." */
+                        char *temp;
                         temp = strchr(ud, '/');
-                        *temp = 0;              /* ~user\0 */
+                        *temp = '\0';           /* ~user\0 */
                         entry = getpwnam(ud);
                         *temp = '/';            /* restore ~user/... */
                         ud = temp;
@@ -1163,21 +1160,23 @@ static void parse_and_put_prompt(const char *prmt_ptr)
         size_t cur_prmt_len = 0;
         char flg_not_length = '[';
         char *prmt_mem_ptr = xzalloc(1);
-        char *pwd_buf = xrealloc_getcwd_or_warn(NULL);
-        char buf2[PATH_MAX + 1];
-        char buf[2];
+        char *cwd_buf = xrealloc_getcwd_or_warn(NULL);
+        char cbuf[2];
         char c;
         char *pbuf;
 
         cmdedit_prmt_len = 0;
 
-        if (!pwd_buf) {
-                pwd_buf = (char *)bb_msg_unknown;
+        if (!cwd_buf) {
+                cwd_buf = (char *)bb_msg_unknown;
         }
 
+        cbuf[1] = '\0'; /* never changes */
+
         while (*prmt_ptr) {
-                pbuf = buf;
-                pbuf[1] = 0;
+                char *free_me = NULL;
+
+                pbuf = cbuf;
                 c = *prmt_ptr++;
                 if (c == '\\') {
                         const char *cp = prmt_ptr;
@@ -1188,6 +1187,7 @@ static void parse_and_put_prompt(const char *prmt_ptr)
                                 if (*cp == '\0')
                                         break;
                                 c = *prmt_ptr++;
+
                                 switch (c) {
 #if ENABLE_FEATURE_GETUSERNAME_AND_HOMEDIR
                                 case 'u':
@@ -1195,87 +1195,81 @@ static void parse_and_put_prompt(const char *prmt_ptr)
                                         break;
 #endif
                                 case 'h':
-                                        pbuf = hostname_buf;
-                                        if (!pbuf) {
-                                                pbuf = xzalloc(256);
-                                                if (gethostname(pbuf, 255) < 0) {
-                                                        strcpy(pbuf, "?");
-                                                } else {
-                                                        char *s = strchr(pbuf, '.');
-                                                        if (s)
-                                                                *s = '\0';
-                                                }
-                                                hostname_buf = pbuf;
+                                        pbuf = free_me = xzalloc(256);
+                                        if (gethostname(pbuf, 255) < 0) {
+                                                pbuf[0] = '?';
+                                                pbuf[1] = '\0';
                                         }
+                                        *strchrnul(pbuf, '.') = '\0';
                                         break;
                                 case '$':
                                         c = (geteuid() == 0 ? '#' : '$');
                                         break;
 #if ENABLE_FEATURE_GETUSERNAME_AND_HOMEDIR
                                 case 'w':
-                                        pbuf = pwd_buf;
+                                        /* /home/user[/something] -> ~[/something] */
+                                        pbuf = cwd_buf;
                                         l = strlen(home_pwd_buf);
                                         if (l != 0
-                                         && strncmp(home_pwd_buf, pbuf, l) == 0
-                                         && (pbuf[l]=='/' || pbuf[l]=='\0')
-                                         && strlen(pwd_buf+l) < PATH_MAX
+                                         && strncmp(home_pwd_buf, cwd_buf, l) == 0
+                                         && (cwd_buf[l]=='/' || cwd_buf[l]=='\0')
+                                         && strlen(cwd_buf + l) < PATH_MAX
                                         ) {
-                                                pbuf = buf2;
-                                                *pbuf = '~';
-                                                strcpy(pbuf+1, pwd_buf+l);
+                                                pbuf = free_me = xasprintf("~%s", cwd_buf + l);
                                         }
                                         break;
 #endif
                                 case 'W':
-                                        pbuf = pwd_buf;
+                                        pbuf = cwd_buf;
                                         cp = strrchr(pbuf, '/');
                                         if (cp != NULL && cp != pbuf)
                                                 pbuf += (cp-pbuf) + 1;
                                         break;
                                 case '!':
-                                        pbuf = buf2;
-                                        snprintf(buf2, sizeof(buf2), "%d", num_ok_lines);
+                                        pbuf = free_me = xasprintf("%d", num_ok_lines);
                                         break;
                                 case 'e': case 'E':     /* \e \E = \033 */
                                         c = '\033';
                                         break;
-                                case 'x': case 'X':
+                                case 'x': case 'X': {
+                                        char buf2[4];
                                         for (l = 0; l < 3;) {
-                                                int h;
+                                                unsigned h;
                                                 buf2[l++] = *prmt_ptr;
-                                                buf2[l] = 0;
-                                                h = strtol(buf2, &pbuf, 16);
+                                                buf2[l] = '\0';
+                                                h = strtoul(buf2, &pbuf, 16);
                                                 if (h > UCHAR_MAX || (pbuf - buf2) < l) {
-                                                        l--;
+                                                        buf2[--l] = '\0';
                                                         break;
                                                 }
                                                 prmt_ptr++;
                                         }
-                                        buf2[l] = 0;
-                                        c = (char)strtol(buf2, NULL, 16);
+                                        c = (char)strtoul(buf2, NULL, 16);
                                         if (c == 0)
                                                 c = '?';
-                                        pbuf = buf;
+                                        pbuf = cbuf;
                                         break;
+                                }
                                 case '[': case ']':
                                         if (c == flg_not_length) {
                                                 flg_not_length = (flg_not_length == '[' ? ']' : '[');
                                                 continue;
                                         }
                                         break;
-                                }
-                        }
-                }
-                if (pbuf == buf)
-                        *pbuf = c;
+                                } /* switch */
+                        } /* if */
+                } /* if */
+                cbuf[0] = c;
                 cur_prmt_len = strlen(pbuf);
                 prmt_len += cur_prmt_len;
                 if (flg_not_length != ']')
                         cmdedit_prmt_len += cur_prmt_len;
                 prmt_mem_ptr = strcat(xrealloc(prmt_mem_ptr, prmt_len+1), pbuf);
-        }
-        if (pwd_buf != (char *)bb_msg_unknown)
-                free(pwd_buf);
+                free(free_me);
+        } /* while */
+
+        if (cwd_buf != (char *)bb_msg_unknown)
+                free(cwd_buf);
         cmdedit_prompt = prmt_mem_ptr;
         put_prompt();
 }
@@ -1397,7 +1391,6 @@ int read_line_input(const char *prompt, char *command, int maxsize, line_input_t
                 if (entry) {
                         user_buf = xstrdup(entry->pw_name);
                         home_pwd_buf = xstrdup(entry->pw_dir);
-                        /* They are not freed on exit (too small to bother) */
                 }
         }
 #endif