libbb: modify find_executable() to not temporarily write to PATH

This allows to simplify "which" applet code

function                                             old     new   delta
find_executable                                       93     111     +18
which_main                                           191     177     -14
builtin_source                                       316     294     -22
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/2 up/down: 18/-36)            Total: -18 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 14 insertions, 21 deletions

diff --git a/shell/hush.c b/shell/hush.c
index 4e477d05a..04dda0734 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -8207,41 +8207,34 @@ static int setup_redirects(struct command *prog, struct squirrel **sqp)
 //TODO: shares code with find_executable() in libbb, factor out?
 static char *find_in_PATH(const char *name)
 {
-        char *ret;
-        const char *PATH = get_local_var_value("PATH");
+        char *p = (char*) get_local_var_value("PATH");
 
-        if (!PATH)
+        if (!p)
                 return NULL;
-        ret = NULL;
         while (1) {
-                const char *end = strchrnul(PATH, ':');
-                int sz = end - PATH; /* must be int! */
+                const char *end = strchrnul(p, ':');
+                int sz = end - p; /* must be int! */
 
-                free(ret);
                 if (sz != 0) {
-                        ret = xasprintf("%.*s/%s", sz, PATH, name);
+                        p = xasprintf("%.*s/%s", sz, p, name);
                 } else {
-                        /* We have xxx::yyyy in $PATH,
+                        /* We have xxx::yyy in $PATH,
                          * it means "use current dir" */
-                        ret = xstrdup(name);
+                        p = xstrdup(name);
                 }
-                if (access(ret, F_OK) == 0)
-                        break;
-
-                if (*end == '\0') {
-                        free(ret);
+                if (access(p, F_OK) == 0)
+                        return p;
+                free(p);
+                if (*end == '\0')
                         return NULL;
-                }
-                PATH = end + 1;
+                p = (char *) end + 1;
         }
-
-        return ret;
 }
 
 #if ENABLE_HUSH_TYPE || ENABLE_HUSH_COMMAND
 static char *find_executable_in_PATH(const char *name)
 {
-        char *PATH;
+        const char *PATH;
         if (strchr(name, '/')) {
                 /* Name with '/' is tested verbatim, with no PATH traversal:
                  * "cd /bin; type ./cat" should print "./cat is ./cat",
@@ -8251,7 +8244,7 @@ static char *find_executable_in_PATH(const char *name)
                         return xstrdup(name);
                 return NULL;
         }
-        PATH = (char*)get_local_var_value("PATH");
+        PATH = get_local_var_value("PATH");
         return find_executable(name, &PATH); /* path == NULL is ok */
 }
 #endif