libbb: fix empty PATH components handling

function                                             old     new   delta
find_execable                                         81      86      +5
exists_execable                                       71      66      -5

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

diff --git a/libbb/execable.c b/libbb/execable.c
index 178a00a5f1f69a762c7f20e5b2dd852bcf2ae2b0..a3caea6f9dbca40a1f532562c35e7e32fbe0ce77 100644 (file)
--- a/libbb/execable.c
+++ b/libbb/execable.c
@@ -30,6 +30,14 @@ int FAST_FUNC execable_file(const char *name)
  */
 char* FAST_FUNC find_execable(const char *filename, char **PATHp)
 {
+       /* About empty components in $PATH:
+        * http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html
+        * 8.3 Other Environment Variables - PATH
+        * A zero-length prefix is a legacy feature that indicates the current
+        * working directory. It appears as two adjacent colons ( "::" ), as an
+        * initial colon preceding the rest of the list, or as a trailing colon
+        * following the rest of the list.
+        */
        char *p, *n;
 
        p = *PATHp;
@@ -37,14 +45,15 @@ char* FAST_FUNC find_execable(const char *filename, char **PATHp)
                n = strchr(p, ':');
                if (n)
                        *n++ = '\0';
-               if (*p != '\0') { /* it's not a PATH="foo::bar" situation */
-                       p = concat_path_file(p, filename);
-                       if (execable_file(p)) {
-                               *PATHp = n;
-                               return p;
-                       }
-                       free(p);
+               p = concat_path_file(
+                       p[0] ? p : ".", /* handle "::" case */
+                       filename
+               );
+               if (execable_file(p)) {
+                       *PATHp = n;
+                       return p;
                }
+               free(p);
                p = n;
        } /* on loop exit p == NULL */
        return p;
@@ -60,11 +69,8 @@ int FAST_FUNC exists_execable(const char *filename)
        char *tmp = path;
        char *ret = find_execable(filename, &tmp);
        free(path);
-       if (ret) {
-               free(ret);
-               return 1;
-       }
-       return 0;
+       free(ret);
+       return ret != NULL;
 }
 
 #if ENABLE_FEATURE_PREFER_APPLETS