Re: Clearing environ

[Todd C. Miller]

On Mon, 25 Apr 2016 16:56:47 -0400, "Ted Unangst" wrote:

> compilers will, however, "miscompile" such code. we should avoid it.

Fair enough.

 - todd

Index: lib/libc/stdlib/setenv.c
===================================================================
RCS file: /cvs/src/lib/libc/stdlib/setenv.c,v
retrieving revision 1.17
diff -u -p -r1.17 setenv.c
--- lib/libc/stdlib/setenv.c    13 Mar 2016 18:34:21 -0000      1.17
+++ lib/libc/stdlib/setenv.c    25 Apr 2016 21:09:20 -0000
@@ -43,7 +43,7 @@ int
 putenv(char *str)
 {
        char **P, *cp;
-       size_t cnt;
+       size_t cnt = 0;
        int offset = 0;
 
        for (cp = str; *cp && *cp != '='; ++cp)
@@ -65,13 +65,15 @@ putenv(char *str)
        }
 
        /* create new slot for string */
-       for (P = environ; *P != NULL; P++)
-               ;
-       cnt = P - environ;
+       if (environ != NULL) {
+               for (P = environ; *P != NULL; P++)
+                       ;
+               cnt = P - environ;
+       }
        P = reallocarray(lastenv, cnt + 2, sizeof(char *));
        if (!P)
                return (-1);
-       if (lastenv != environ)
+       if (lastenv != environ && environ != NULL)
                memcpy(P, environ, cnt * sizeof(char *));
        lastenv = environ = P;
        environ[cnt] = str;
@@ -122,15 +124,17 @@ setenv(const char *name, const char *val
                                        break;
                }
        } else {                                        /* create new slot */
-               size_t cnt;
+               size_t cnt = 0;
 
-               for (P = environ; *P != NULL; P++)
-                       ;
-               cnt = P - environ;
+               if (environ != NULL) {
+                       for (P = environ; *P != NULL; P++)
+                               ;
+                       cnt = P - environ;
+               }
                P = reallocarray(lastenv, cnt + 2, sizeof(char *));
                if (!P)
                        return (-1);
-               if (lastenv != environ)
+               if (lastenv != environ && environ != NULL)
                        memcpy(P, environ, cnt * sizeof(char *));
                lastenv = environ = P;
                offset = cnt;