Identify the few unsafe narrowing conversions from sampleCount...

... I believe this list of four places is exhaustive.

There are many, many more safe narrowings that I examined.

This resulted from changing the definition of sampleCount in my builds so that
narrowing conversions failed to compile without some fixes, and I examined and
fixed every place.

The rest of that work is not yet shared.

src/effects/SBSMSEffect.cpp

@@ -334,11 +334,15 @@ bool EffectSBSMS::Process()
                                       (long)((float)(processPresamples)*(srTrack/srProcess)));
               rb.offset = start - trackPresamples;
               rb.end = trackEnd;
-              rb.iface = std::make_unique<SBSMSEffectInterface>(rb.resampler.get(),
-                                                      &rateSlide,&pitchSlide,
-                                                      bPitchReferenceInput,
-                                                      samplesToProcess,processPresamples,
-                                                      rb.quality.get());
+              rb.iface = std::make_unique<SBSMSEffectInterface>
+                  (rb.resampler.get(), &rateSlide, &pitchSlide,
+                   bPitchReferenceInput,
+                   // UNSAFE_SAMPLE_COUNT_TRUNCATION
+                   // The argument type is only long!
+                   static_cast<long> ( static_cast<size_t> (
+                        samplesToProcess ) ),
+                   processPresamples,
+                   rb.quality.get());
             }
             
             Resampler resampler(outResampleCB,&rb,outSlideType);

src/effects/nyquist/Nyquist.cpp

@@ -86,7 +86,7 @@ enum
 };
 
 // Protect Nyquist from selections greater than 2^31 samples (bug 439)
-#define NYQ_MAX_LEN ((sampleCount) 2147483647)
+#define NYQ_MAX_LEN (std::numeric_limits<long>::max())
 
 #define UNINITIALIZED_CONTROL ((double)99999999.99)
 
@@ -630,8 +630,12 @@ bool NyquistEffect::Process()
          mCurLen = (sampleCount)(end - mCurStart[0]);
 
          if (mCurLen > NYQ_MAX_LEN) {
-            wxMessageBox(_("Selection too long for Nyquist code.\nMaximum allowed selection is 2147483647 samples\n(about 13.5 hours at 44100 Hz sample rate)."),
-                         _("Nyquist Error"), wxOK | wxCENTRE);
+            float hours = (float)NYQ_MAX_LEN / (44100 * 60 * 60);
+            const auto message = wxString::Format(
+_("Selection too long for Nyquist code.\nMaximum allowed selection is %ld samples\n(about %.1f hours at 44100 Hz sample rate)."),
+               (long)NYQ_MAX_LEN, hours
+            );
+            wxMessageBox(message, _("Nyquist Error"), wxOK | wxCENTRE);
             if (!mProjectChanged)
                em.SetSkipStateFlag(true);
             return false;
@@ -959,11 +963,21 @@ bool NyquistEffect::ProcessOne()
       nyx_set_audio_params(mCurTrack[0]->GetRate(), 0);
    }
    else {
-      nyx_set_audio_params(mCurTrack[0]->GetRate(), mCurLen);
+      // UNSAFE_SAMPLE_COUNT_TRUNCATION
+      // Danger!  Truncation of long long to long!
+      // Don't say we didn't warn you!
+
+      // Note mCurLen was elsewhere limited to mMaxLen, which is normally
+      // the greatest long value, and yet even mMaxLen may be experimentally
+      // increased with a nyquist comment directive.
+      // See the parsing of "maxlen"
+
+      auto curLen = (long)(static_cast<long long>(mCurLen));
+      nyx_set_audio_params(mCurTrack[0]->GetRate(), curLen);
 
       nyx_set_input_audio(StaticGetCallback, (void *)this,
                           mCurNumChannels,
-                          mCurLen, mCurTrack[0]->GetRate());
+                          curLen, mCurTrack[0]->GetRate());
    }
 
    // Restore the Nyquist sixteenth note symbol for Generate plugins.

src/effects/vamp/VampEffect.cpp

@@ -522,7 +522,12 @@ bool VampEffect::Process()
             }
          }
 
-         Vamp::RealTime timestamp = Vamp::RealTime::frame2RealTime(ls, (int)(mRate + 0.5));
+         // UNSAFE_SAMPLE_COUNT_TRUNCATION
+         // Truncation in case of very long tracks!
+         Vamp::RealTime timestamp = Vamp::RealTime::frame2RealTime(
+            (long) static_cast<long long>( ls ),
+            (int)(mRate + 0.5)
+         );
 
          Vamp::Plugin::FeatureSet features = mPlugin->process(data, timestamp);
          AddFeatures(ltrack, features);

src/widgets/NumericTextCtrl.cpp

@@ -848,7 +848,9 @@ void NumericConverter::ValueToControls(double rawValue, bool nearest /* = true *
       }
       else {
          if (t_int >= 0) {
-            value = (t_int / mFields[i].base);
+            // UNSAFE_SAMPLE_COUNT_TRUNCATION
+            // truncation danger!
+            value = (static_cast<long long>( t_int ) / mFields[i].base);
             if (mFields[i].range > 0)
                value = value % mFields[i].range;
          }