Use memmove() not memcpy() to slide some pointers down.

The previous coding here was formally undefined, though it seems to
accidentally work on most platforms in the buildfarm.  Caught by some
OpenBSD platforms in which libc contains an assertion check for
overlapping areas passed to memcpy().

Thomas Munro

src/test/isolation/isolationtester.c

@@ -554,8 +554,8 @@ run_permutation(TestSpec *testspec, int nsteps, Step **steps)
 
 				/* Remove that step from the waiting[] array. */
 				if (w + 1 < nwaiting)
-					memcpy(&waiting[w], &waiting[w + 1],
-						   (nwaiting - (w + 1)) * sizeof(Step *));
+					memmove(&waiting[w], &waiting[w + 1],
+							(nwaiting - (w + 1)) * sizeof(Step *));
 				nwaiting--;
 
 				break;
@@ -582,8 +582,8 @@ run_permutation(TestSpec *testspec, int nsteps, Step **steps)
 					/* This one finished, too! */
 					errorstep[nerrorstep++] = waiting[w];
 					if (w + 1 < nwaiting)
-						memcpy(&waiting[w], &waiting[w + 1],
-							   (nwaiting - (w + 1)) * sizeof(Step *));
+						memmove(&waiting[w], &waiting[w + 1],
+								(nwaiting - (w + 1)) * sizeof(Step *));
 					nwaiting--;
 				}
 			}
@@ -614,8 +614,8 @@ run_permutation(TestSpec *testspec, int nsteps, Step **steps)
 			{
 				errorstep[nerrorstep++] = waiting[w];
 				if (w + 1 < nwaiting)
-					memcpy(&waiting[w], &waiting[w + 1],
-						   (nwaiting - (w + 1)) * sizeof(Step *));
+					memmove(&waiting[w], &waiting[w + 1],
+							(nwaiting - (w + 1)) * sizeof(Step *));
 				nwaiting--;
 			}
 		}