diff --git a/test/test_real.c b/test/test_real.c
index 52e9be8..e7a0dd9 100644
--- a/test/test_real.c
+++ b/test/test_real.c
@@ -85,8 +85,13 @@ int main(int argc,char ** argv)
     int nfft = 8*3*5;
     double ts,tfft,trfft;
     int i;
-    if (argc>1)
+    if (argc>1) {
         nfft = atoi(argv[1]);
+        if (nfft <= 0) {
+            fprintf(stderr,"Error: nfft must be a positive integer\n");
+            return 1;
+        }
+    }
     kiss_fft_cpx cin[nfft];
     kiss_fft_cpx cout[nfft];
     kiss_fft_cpx sout[nfft];
diff --git a/test/testcpp.cc b/test/testcpp.cc
index 50acada..5715a3f 100644
--- a/test/testcpp.cc
+++ b/test/testcpp.cc
@@ -25,6 +25,11 @@ using namespace std;
 template <class T>
 void dotest(int nfft)
 {
+    if (nfft <= 0) {
+        cerr << "invalid nfft:" << nfft << endl;
+        return;
+    }
+
     typedef kissfft<T> FFT;
     typedef std::complex<T> cpx_type;
 
@@ -59,7 +64,8 @@ void dotest(int nfft)
         complex<long double> dif = acc - x;
         difpower += norm(dif);
     }
-    cout << " RMSE:" << sqrt(difpower/totalpower) << "\t";
+    const long double denom = (totalpower > 0) ? totalpower : 1e-30L;
+    cout << " RMSE:" << sqrt(difpower/denom) << "\t";
 
     double t0 = curtime();
     int nits=20e6/nfft;
diff --git a/test/testkiss.py b/test/testkiss.py
index 474de4d..2e69330 100755
--- a/test/testkiss.py
+++ b/test/testkiss.py
@@ -100,15 +100,14 @@ def dofft(x, isreal):
         x = 2147483647.0 * x
         scale = len(x) / 2147483647.0
 
-    cmd = util + ' -n '
-    cmd += ','.join([str(d) for d in dims])
+    cmd = [util, '-n', ','.join([str(d) for d in dims])]
     if do_real:
-        cmd += ' -R '
+        cmd.append('-R')
 
-    print(cmd)
+    print(' '.join(cmd))
 
     from subprocess import Popen, PIPE
-    p = Popen(cmd, shell=True, stdin=PIPE, stdout=PIPE)
+    p = Popen(cmd, stdin=PIPE, stdout=PIPE)
 
     p.stdin.write(dopack(x))
     p.stdin.close()
diff --git a/test/twotonetest.c b/test/twotonetest.c
index e93fac3..66a0b63 100644
--- a/test/twotonetest.c
+++ b/test/twotonetest.c
@@ -75,6 +75,9 @@ double two_tone_test( int nfft, int bin1,int bin2)
             sigpow += mag2;
     }
     kiss_fft_cleanup();
+    free(cfg);
+    free(tbuf);
+    free(kout);
     /*printf("TEST %d,%d,%d noise @ %fdB\n",nfft,bin1,bin2,10*log10(noisepow/sigpow +1e-30) );*/
     return 10*log10(sigpow/(noisepow+1e-50) );
 }
@@ -82,7 +85,13 @@ double two_tone_test( int nfft, int bin1,int bin2)
 int main(int argc,char ** argv)
 {
     int nfft = 4*2*2*3*5;
-    if (argc>1) nfft = atoi(argv[1]);
+    if (argc>1) {
+        nfft = atoi(argv[1]);
+        if (nfft <= 0) {
+            fprintf(stderr,"Error: nfft must be a positive integer\n");
+            return 1;
+        }
+    }
 
     int i,j;
     double minsnr = 500;
diff --git a/tools/fftutil.c b/tools/fftutil.c
index 2d947d6..ef9be29 100644
--- a/tools/fftutil.c
+++ b/tools/fftutil.c
@@ -26,9 +26,16 @@ void fft_file(FILE * fin,FILE * fout,int nfft,int isinverse)
     bufout = (kiss_fft_cpx*)malloc(sizeof(kiss_fft_cpx) * nfft );
     st = kiss_fft_alloc( nfft ,isinverse ,0,0);
 
-    while ( fread( buf , sizeof(kiss_fft_cpx) * nfft ,1, fin ) > 0 ) {
-        kiss_fft( st , buf ,bufout);
-        fwrite( bufout , sizeof(kiss_fft_cpx) , nfft , fout );
+    while (1) {
+        size_t nread = fread(buf, sizeof(kiss_fft_cpx), nfft, fin);
+        if (nread == (size_t)nfft) {
+            kiss_fft( st , buf ,bufout);
+            fwrite( bufout , sizeof(kiss_fft_cpx) , nfft , fout );
+            continue;
+        }
+        if (nread != 0)
+            fprintf(stderr,"short read on complex input\n");
+        break;
     }
     free(st);
     free(buf);
@@ -47,9 +54,16 @@ void fft_filend(FILE * fin,FILE * fout,int *dims,int ndims,int isinverse)
     buf = (kiss_fft_cpx *) malloc (sizeof (kiss_fft_cpx) * dimprod);
     st = kiss_fftnd_alloc (dims, ndims, isinverse, 0, 0);
 
-    while (fread (buf, sizeof (kiss_fft_cpx) * dimprod, 1, fin) > 0) {
-        kiss_fftnd (st, buf, buf);
-        fwrite (buf, sizeof (kiss_fft_cpx), dimprod, fout);
+    while (1) {
+        size_t nread = fread(buf, sizeof(kiss_fft_cpx), dimprod, fin);
+        if (nread == (size_t)dimprod) {
+            kiss_fftnd(st, buf, buf);
+            fwrite(buf, sizeof(kiss_fft_cpx), dimprod, fout);
+            continue;
+        }
+        if (nread != 0)
+            fprintf(stderr,"short read on nd complex input\n");
+        break;
     }
     free (st);
     free (buf);
@@ -81,17 +95,24 @@ void fft_filend_real(FILE * fin,FILE * fout,int *dims,int ndims,int isinverse)
 
     st = kiss_fftndr_alloc(dims, ndims, isinverse, 0, 0);
 
-    while ( fread (ibuf, sizeof(kiss_fft_scalar), insize,  fin) > 0) {
-        if (isinverse) {
-            kiss_fftndri(st,
-                    (kiss_fft_cpx*)ibuf,
-                    (kiss_fft_scalar*)obuf);
-        }else{
-            kiss_fftndr(st,
-                    (kiss_fft_scalar*)ibuf,
-                    (kiss_fft_cpx*)obuf);
+    while (1) {
+        size_t nread = fread(ibuf, sizeof(kiss_fft_scalar), insize, fin);
+        if (nread == (size_t)insize) {
+            if (isinverse) {
+                kiss_fftndri(st,
+                        (kiss_fft_cpx*)ibuf,
+                        (kiss_fft_scalar*)obuf);
+            } else {
+                kiss_fftndr(st,
+                        (kiss_fft_scalar*)ibuf,
+                        (kiss_fft_cpx*)obuf);
+            }
+            fwrite(obuf, sizeof(kiss_fft_scalar), outsize, fout);
+            continue;
         }
-        fwrite (obuf, sizeof(kiss_fft_scalar), outsize,fout);
+        if (nread != 0)
+            fprintf(stderr,"short read on nd real input\n");
+        break;
     }
     free(st);
     free(ibuf);
@@ -110,14 +131,28 @@ void fft_file_real(FILE * fin,FILE * fout,int nfft,int isinverse)
     st = kiss_fftr_alloc( nfft ,isinverse ,0,0);
 
     if (isinverse==0) {
-        while ( fread( rbuf , sizeof(kiss_fft_scalar) * nfft ,1, fin ) > 0 ) {
-            kiss_fftr( st , rbuf ,cbuf);
-            fwrite( cbuf , sizeof(kiss_fft_cpx) , (nfft/2 + 1) , fout );
+        while (1) {
+            size_t nread = fread(rbuf, sizeof(kiss_fft_scalar), nfft, fin);
+            if (nread == nfft) {
+                kiss_fftr( st , rbuf ,cbuf);
+                fwrite( cbuf , sizeof(kiss_fft_cpx) , (nfft/2 + 1) , fout );
+                continue;
+            }
+            if (nread != 0)
+                fprintf(stderr,"short read on real input\n");
+            break;
         }
     }else{
-        while ( fread( cbuf , sizeof(kiss_fft_cpx) * (nfft/2+1) ,1, fin ) > 0 ) {
-            kiss_fftri( st , cbuf ,rbuf);
-            fwrite( rbuf , sizeof(kiss_fft_scalar) , nfft , fout );
+        while (1) {
+            size_t nread = fread(cbuf, sizeof(kiss_fft_cpx), (nfft/2+1), fin);
+            if (nread == (size_t)(nfft/2+1)) {
+                kiss_fftri( st , cbuf ,rbuf);
+                fwrite( rbuf , sizeof(kiss_fft_scalar) , nfft , fout );
+                continue;
+            }
+            if (nread != 0)
+                fprintf(stderr,"short read on complex input\n");
+            break;
         }
     }
     free(st);
diff --git a/tools/kiss_fastfir.c b/tools/kiss_fastfir.c
index e066328..a7e81d8 100644
--- a/tools/kiss_fastfir.c
+++ b/tools/kiss_fastfir.c
@@ -377,7 +377,6 @@ void do_file_filter(
     cfg=kiss_fastfir_alloc(imp_resp,n_imp_resp,&nfft,0,0);
 
     /* use length to minimize buffer shift*/
-    n_samps_buf = 8*4096/sizeof(kffsamp_t); 
     n_samps_buf = nfft + 4*(nfft-n_imp_resp+1);
 
     if (verbose) fprintf(stderr,"bufsize=%d\n",(int)(sizeof(kffsamp_t)*n_samps_buf) );
@@ -466,12 +465,31 @@ int main(int argc,char**argv)
         exit(1);
     }
     fseek(filtfile,0,SEEK_END);
-    nh = ftell(filtfile) / sizeof(kffsamp_t);
+    {
+        long filt_bytes = ftell(filtfile);
+        if (filt_bytes < 0) {
+            fprintf(stderr,"could not determine filter file size\n");
+            exit(1);
+        }
+        if ((size_t)filt_bytes < sizeof(kffsamp_t)) {
+            fprintf(stderr,"filter file too small\n");
+            exit(1);
+        }
+        nh = (size_t)filt_bytes / sizeof(kffsamp_t);
+    }
     if (verbose) fprintf(stderr,"%d samples in FIR filter\n",(int)nh);
     h = (kffsamp_t*)malloc(sizeof(kffsamp_t)*nh);
+    if (h == NULL) {
+        fprintf(stderr,"failed to allocate filter coefficients\n");
+        exit(1);
+    }
     fseek(filtfile,0,SEEK_SET);
     if (fread(h,sizeof(kffsamp_t),nh,filtfile) != nh)
-        fprintf(stderr,"short read on filter file\n");
+        {
+            fprintf(stderr,"short read on filter file\n");
+            free(h);
+            exit(1);
+        }
 
     fclose(filtfile);