Don't modify variables in the child since we vfork()'d to

get there (address space is shared between parent in child
in traditional vfork(2)).  From FreeBSD (dyson).

diff --git a/lib/libc/gen/popen.c b/lib/libc/gen/popen.c
index 56a6898..2b66760 100644 (file)
--- a/lib/libc/gen/popen.c
+++ b/lib/libc/gen/popen.c
@@ -35,7 +35,7 @@
  */
 
 #if defined(LIBC_SCCS) && !defined(lint)
-static char rcsid[] = "$OpenBSD: popen.c,v 1.3 1996/08/19 08:25:20 tholo Exp $";
+static char rcsid[] = "$OpenBSD: popen.c,v 1.4 1997/04/16 21:59:04 millert Exp $";
 #endif /* LIBC_SCCS and not lint */
 
 #include <sys/param.h>
@@ -86,9 +86,15 @@ popen(program, type)
                /* NOTREACHED */
        case 0:                         /* Child. */
                if (*type == 'r') {
-                       if (pdes[1] != STDOUT_FILENO) {
-                               (void)dup2(pdes[1], STDOUT_FILENO);
-                               (void)close(pdes[1]);
+                       /*
+                        * We must NOT modify pdes, due to the
+                        * semantics of vfork.
+                        */
+                       int tpdes1 = pdes[1];
+                       if (tpdes1 != STDOUT_FILENO) {
+                               (void)dup2(tpdes1, STDOUT_FILENO);
+                               (void)close(tpdes1);
+                               tpdes1 = STDOUT_FILENO;
                        }
                        (void) close(pdes[0]);
                } else {