diff --git a/sources/checkpoint.c b/sources/checkpoint.c
index 58597d43..ce318fe8 100644
--- a/sources/checkpoint.c
+++ b/sources/checkpoint.c
@@ -1420,10 +1420,16 @@ int DoRecovery(int *moduletype)
 	if ( !(fd = fopen(recoveryfile, "r")) ) return(__LINE__);
 
 	/* load the complete recovery file into a buffer */
-	if ( fread(&pos, sizeof(POSITION), 1, fd) != 1 ) return(__LINE__);
+	if ( fread(&pos, sizeof(POSITION), 1, fd) != 1 ) {
+		fclose(fd);
+		return(__LINE__);
+	}
 	size = BASEPOSITION(pos) - sizeof(POSITION);
 	buf = Malloc1(size, "recovery buffer");
-	if ( fread(buf, size, 1, fd) != 1 ) return(__LINE__);
+	if ( fread(buf, size, 1, fd) != 1 ) {
+		fclose(fd);
+		return(__LINE__);
+	}
 
 	/* pointer p will go through the buffer in the following */
 	p = buf;
@@ -2478,7 +2484,7 @@ static int DoSnapshot(int moduletype)
 {
 	GETIDENTITY
 	FILE *fd;
-	POSITION pos;
+	POSITION pos = {0};
 	int i, j;
 	LONG l;
 	WORD *w;
@@ -2495,10 +2501,16 @@ static int DoSnapshot(int moduletype)
 	if ( !(fd = fopen(intermedfile, "wb")) ) return(__LINE__);
 
 	/* reserve space in the file for a length field */
-	if ( fwrite(&pos, 1, sizeof(POSITION), fd) != sizeof(POSITION) ) return(__LINE__);
+	if ( fwrite(&pos, 1, sizeof(POSITION), fd) != sizeof(POSITION) ) {
+		fclose(fd);
+		return(__LINE__);
+	}
 
 	/* write moduletype */
-	if ( fwrite(&moduletype, 1, sizeof(int), fd) != sizeof(int) ) return(__LINE__);
+	if ( fwrite(&moduletype, 1, sizeof(int), fd) != sizeof(int) ) {
+		fclose(fd);
+		return(__LINE__);
+	}
 
 	/*#[ AM :*/
 
diff --git a/sources/minos.c b/sources/minos.c
index 7a525d93..0268379f 100644
--- a/sources/minos.c
+++ b/sources/minos.c
@@ -622,6 +622,7 @@ DBASE *NewDbase(char *name,MLONG number)
 	if ( ( d->iblocks = (INDEXBLOCK **)Malloc1(numblocks*sizeof(INDEXBLOCK *),
 	"new database") ) == 0 ) {
 		NumTableBases--;
+		fclose(f);
 		return(0);
 	}
 	d->tablenames = 0;
@@ -635,6 +636,7 @@ DBASE *NewDbase(char *name,MLONG number)
 	"new database") ) == 0 ) {
 		M_free(d->iblocks,"new database");
 		NumTableBases--;
+		fclose(f);
 		return(0);
 	}
 	if ( ( f = fopen(name,"w+b") ) == 0 ) {
diff --git a/sources/parallel.c b/sources/parallel.c
index e2fd504b..39a577b5 100644
--- a/sources/parallel.c
+++ b/sources/parallel.c
@@ -4681,7 +4681,7 @@ static void PF_BroadcastRuntimeError(void)
 {
 	assert(PF.me == MASTER);
 
-	int ret, dummy;
+	int ret, dummy = 0;
 	MPI_Request requests[PF.numtasks - 1];
 
 	/*
diff --git a/sources/ratio.c b/sources/ratio.c
index 6c8a70bf..d63b7fad 100644
--- a/sources/ratio.c
+++ b/sources/ratio.c
@@ -3108,14 +3108,15 @@ char *TheErrorMessage[] = {
 	,"Irregular code in PolyRatFun encountered in ExpandRat."
 	,"Called from ExpandRat."
 	,"WorkSpace overflow. Change parameter WorkSpace in setup file?"
+	,"Illegal term in expanded polyratfun."
 	};
 
 int ExpandRat(PHEAD WORD *fun)
 {
-	WORD *r, *rr, *rrr, *tt, *tnext, *arg1, *arg2, *rmin = 0, *rmininv;
+	WORD *r, *rr, *rrr, *tt, *tnext, *arg1, *arg2, *rmin = NULL, *rmininv;
 	WORD *rcoef, rsize, rcopy, *ow = AT.WorkPointer;
 	WORD *numerator, *denominator, *rnext;
-	WORD *thecopy, *rc, ncoef, newcoef, *m, *mm, nco, *outarg = 0;
+	WORD *thecopy, *rc, ncoef, newcoef, *m, *mm, nco, *outarg = NULL;
 	UWORD co[2], co1[2], co2[2];
 	WORD OldPolyFunPow = AR.PolyFunPow;
 	int i, j, minpow = 0, eppow, first, error = 0, ipoly;
@@ -3127,7 +3128,7 @@ int ExpandRat(PHEAD WORD *fun)
 		We have to normalize the argument. This could make it shorter.
 */
 NormArg:;
-		if ( outarg == 0 ) outarg = TermMalloc("ExpandRat")+ARGHEAD;
+		if ( outarg == NULL ) outarg = TermMalloc("ExpandRat")+ARGHEAD;
 		AT.TrimPower = 1;
 		NewSort(BHEAD0);
 		r = fun+FUNHEAD+ARGHEAD;
@@ -3145,10 +3146,7 @@ NormArg:;
 					if ( rrm[1] == SYMBOL && rrm[2] == 4 && rrm[3] == AR.PolyFunVar ) {
 						if ( rrm[4] < minpow2 ) minpow2 = rrm[4];
 					}
-					else {
-						MesPrint("Illegal term in expanded polyratfun.");
-						goto onerror;
-					}
+					else { error = 5; goto onerror; }
 				}
 				rrm += *rrm;
 			}
@@ -3185,15 +3183,15 @@ NormArg:;
 	First test whether we have only AR.PolyFunVar in the denominator
 */
 	tt = fun + FUNHEAD;
-	arg1 = arg2 = 0;
+	arg1 = arg2 = NULL;
 	if ( tt < tnext ) {
 		arg1 = tt; NEXTARG(tt);
 		if ( tt < tnext ) {
 			arg2 = tt; NEXTARG(tt);
-			if ( tt != tnext ) { arg1 = arg2 = 0; } /* more than two arguments */
+			if ( tt != tnext ) { arg1 = arg2 = NULL; } /* more than two arguments */
 		}
-	}
-	if ( arg2 == 0 ) {
+	} else { error = 5; goto onerror; }
+	if ( arg2 == NULL ) {
 		if ( *arg1 < 0 ) { fun[2] = CLEANFLAG; goto done; }
 		if ( fun[2] == CLEANFLAG ) goto done;
 		goto NormArg;   /* Note: should not come here */
@@ -3201,7 +3199,7 @@ NormArg:;
 /*
 	Produce the output argument in outarg
 */
-	if ( outarg == 0 ) outarg = TermMalloc("ExpandRat")+ARGHEAD;
+	if ( outarg == NULL ) outarg = TermMalloc("ExpandRat")+ARGHEAD;
 
 	if ( *arg2 <= 0 ) {
 /*
@@ -3256,10 +3254,7 @@ NormArg:;
 							if ( rrm[1] == SYMBOL && rrm[2] == 4 && rrm[3] == AR.PolyFunVar ) {
 								if ( rrm[4] < minpow2 ) minpow2 = rrm[4];
 							}
-							else {
-								MesPrint("Illegal term in expanded polyratfun.");
-								goto onerror;
-							}
+							else { error = 5; goto onerror; }
 						}
 						rrm += *rrm;
 					}
@@ -3336,10 +3331,7 @@ NormArg:;
 							if ( rrm[1] == SYMBOL && rrm[2] == 4 && rrm[3] == AR.PolyFunVar ) {
 								if ( rrm[4] < minpow2 ) minpow2 = rrm[4];
 							}
-							else {
-								MesPrint("Illegal term in expanded polyratfun.");
-								goto onerror;
-							}
+							else { error = 5; goto onerror; }
 						}
 						rrm += *rrm;
 					}
diff --git a/sources/reken.c b/sources/reken.c
index 902856a4..70f2cc2e 100644
--- a/sources/reken.c
+++ b/sources/reken.c
@@ -1246,7 +1246,7 @@ int RaisPow(PHEAD UWORD *a, WORD *na, UWORD b)
 		c /= 2;
 	}
 	i--;
-	c = 1 << i;
+	c = 1u << i;
 	while ( --i >= 0 ) {
 		c /= 2;
 		if(MulLong(is,ns,is,ns,it,&nt)) goto RaisOvl;
diff --git a/sources/setfile.c b/sources/setfile.c
index d15bb654..e8a594f0 100644
--- a/sources/setfile.c
+++ b/sources/setfile.c
@@ -278,11 +278,11 @@ restart:;
 				break;
 			case PATHVALUE:
 				if ( StrICmp(s1,(UBYTE *)"incdir") == 0 ) {
-					AM.IncDir = 0;
+					AM.IncDir = NULL;
 				}
 				else if ( StrICmp(s1,(UBYTE *)"path") == 0 ) {
 					if ( AM.Path ) M_free(AM.Path,"path");
-					AM.Path = 0;
+					AM.Path = NULL;
 				}
 				else {
 					MesPrint("Setups: %s not yet implemented",s1);
@@ -775,16 +775,16 @@ int AllocSetups(void)
 /*
 	And now some order sensitive things
 */
-	if ( AM.Path == 0 ) {
+	if ( AM.Path == NULL ) {
 		sp = GetSetupPar((UBYTE *)"path");
 		AM.Path = strDup1((UBYTE *)(sp->value),"path");
 	}
-	if ( AM.IncDir == 0 ) {
+	if ( AM.IncDir == NULL ) {
 		sp = GetSetupPar((UBYTE *)"incdir");
 		AM.IncDir = strDup1((UBYTE *)(sp->value),"incdir");
 	}
 /*
-	if ( AM.TempDir == 0 ) {
+	if ( AM.TempDir == NULL ) {
 		sp = GetSetupPar((UBYTE *)"tempdir");
 		AM.TempDir = strDup1((UBYTE *)(sp->value),"tempdir");
 	}
diff --git a/sources/startup.c b/sources/startup.c
index 6f85902d..126b7d3b 100644
--- a/sources/startup.c
+++ b/sources/startup.c
@@ -290,7 +290,7 @@ int DoTail(int argc, UBYTE **argv)
 	AM.LogType = -1;
 	AM.HoldFlag = AM.qError = AM.Interact = AM.FileOnlyFlag = 0;
 	AM.InputFileName = AM.LogFileName = AM.IncDir = AM.TempDir = AM.TempSortDir =
-	AM.SetupDir = AM.SetupFile = AM.Path = 0;
+	AM.SetupDir = AM.SetupFile = AM.Path = NULL;
 	AM.FromStdin = 0;
 	/* Always use MultiRun, "-M" option is now ignored. */
 	AM.MultiRun = 1;
@@ -538,7 +538,7 @@ printversion:;
 			while ( *s ) *t++ = *s++;
 			*t++ = '.'; *t++ = 'f'; *t++ = 'r'; *t++ = 'm'; *t = 0;
 		}
-		if ( AM.LogType >= 0 && AM.LogFileName == 0 ) {
+		if ( AM.LogType >= 0 && AM.LogFileName == NULL ) {
 			AM.LogFileName = strDup1(AM.InputFileName,"name of logfile");
 			s = AM.LogFileName;
 			while ( *s ) s++;
@@ -567,7 +567,7 @@ printversion:;
 		printf("No filename specified in call of FORM\n");
 		errorflag++;
 	}
-	if ( AM.Path == 0 ) AM.Path = (UBYTE *)getenv("FORMPATH");
+	if ( AM.Path == NULL ) AM.Path = (UBYTE *)getenv("FORMPATH");
 	if ( AM.Path ) {
 		/*
 		 * AM.Path is taken from argv or getenv. Reallocate it to avoid invalid
@@ -718,22 +718,22 @@ void ReserveTempFiles(int par)
 	int i = 0;
 	WORD j;
 	if ( par == 0 || par == 1 ) {
-	if ( AM.TempDir == 0 ) {
+	if ( AM.TempDir == NULL ) {
 		sp = GetSetupPar((UBYTE *)"tempdir");
 		if ( ( sp->flags & USEDFLAG ) != USEDFLAG ) {
 			AM.TempDir = (UBYTE *)getenv("FORMTMP");
-			if ( AM.TempDir == 0 ) AM.TempDir = emptystring;
+			if ( AM.TempDir == NULL ) AM.TempDir = emptystring;
 		}
 		else AM.TempDir = (UBYTE *)(sp->value);
 	}
-	if ( AM.TempSortDir == 0 ) {
+	if ( AM.TempSortDir == NULL ) {
 		if ( AM.havesortdir ) {
 			sp = GetSetupPar((UBYTE *)"tempsortdir");
 			AM.TempSortDir = (UBYTE *)(sp->value);
 		}
 		else {
 			AM.TempSortDir = (UBYTE *)getenv("FORMTMPSORT");
-			if ( AM.TempSortDir == 0 ) AM.TempSortDir = AM.TempDir;
+			if ( AM.TempSortDir == NULL ) AM.TempSortDir = AM.TempDir;
 		}
 	}
 /*
diff --git a/sources/tools.c b/sources/tools.c
index f63025b4..db2aeeeb 100644
--- a/sources/tools.c
+++ b/sources/tools.c
@@ -1123,6 +1123,7 @@ int CopyFile(char *source, char *dest)
 	}
 	out = fopen(dest, "wb");
 	if ( out == NULL ) {
+		fclose(in);
 		perror("CopyFile: ");
 		return(2);
 	}