http://lists.pld-linux.org/mailman/pipermail/pld-devel-en/2015-November/thread.html#24537

--- rpm-5.4.15.orig/rpmio/macro.c	2015-11-28 20:47:15.000000000 +0100
+++ rpm-5.4.15/rpmio/macro.c	2015-11-28 20:51:05.634724202 +0100
@@ -706,7 +706,9 @@
     FILE *shf;
     int rc;
     int c;
+    char * start;
 
+    start = mb->t;
     strncpy(buf, cmd, clen);
     buf[clen] = '\0';
     rc = expandU(mb, buf, bufn);
@@ -720,7 +722,7 @@
     (void) pclose(shf);
 
     /* XXX delete trailing \r \n */
-    while (iseol(mb->t[-1])) {
+    while (mb->t > start && iseol(mb->t[-1])) {
 	*(mb->t--) = '\0';
 	mb->nb++;
     }