Handle divisions by 0 in Lb302 and Monstro (#7021)

* Handle divisions by 0 in Lb302

Handle potential division by 0 which in turn lead to floating point exceptions in Lb302. The division can occur in the `process` method if it is called with the member `vco_inc` still initialized to 0. This seems to happen then the Lb302 processes with no notes actually being played.

The offending call is `BandLimitedWave::pdToLen(vco_inc)` which is now prevented when the increment is 0. In the latter case a sample of 0 is produced. This works because in all other cases the Lb302 instance should process a note which in turn sets the increments to something different from 0.

* Fix FPEs in Monstro

Fix some floating point exceptions in `MonstroSynth::renderOutput` that occurred due to calling `BandLimitedWave::pdToLen` with a value of 0. This happened when one of the phase deltas was set to 0, i.e. `pd_l` or `pd_r`. These cases are now checked and produce silence in the corresponding components if the phase delta is set to 0.

* Fix uninitialized variables

Initialize the local variables `len_l` and `len_r` to 0. This fixes compiler warnings a la "error: 'len_r' may be used uninitialized in this function" which are treated as errors on the build server.

* Adjust whitespace of touched code

plugins/Lb302/Lb302.cpp

@@ -585,20 +585,23 @@ int Lb302Synth::process(sampleFrame *outbuf, const int size)
 				vco_k = 0.5 * Oscillator::noiseSample( vco_c );
 				break;
 
+			// The next cases all use the BandLimitedWave class which uses the oscillator increment `vco_inc` to compute samples.
+			// If that oscillator increment is 0 we return a 0 sample because calling BandLimitedWave::pdToLen(0) leads to a
+			// division by 0 which in turn leads to floating point exceptions.
 			case VcoShape::BLSawtooth:
-				vco_k = BandLimitedWave::oscillate( vco_c + 0.5f, BandLimitedWave::pdToLen( vco_inc ), BandLimitedWave::Waveform::BLSaw ) * 0.5f;
+				vco_k = vco_inc == 0. ? 0. : BandLimitedWave::oscillate(vco_c + 0.5f, BandLimitedWave::pdToLen(vco_inc), BandLimitedWave::Waveform::BLSaw) * 0.5f;
 				break;
 
 			case VcoShape::BLSquare:
-				vco_k = BandLimitedWave::oscillate( vco_c + 0.5f, BandLimitedWave::pdToLen( vco_inc ), BandLimitedWave::Waveform::BLSquare ) * 0.5f;
+				vco_k = vco_inc == 0. ? 0. : BandLimitedWave::oscillate(vco_c + 0.5f, BandLimitedWave::pdToLen(vco_inc), BandLimitedWave::Waveform::BLSquare) * 0.5f;
 				break;
 
 			case VcoShape::BLTriangle:
-				vco_k = BandLimitedWave::oscillate( vco_c + 0.5f, BandLimitedWave::pdToLen( vco_inc ), BandLimitedWave::Waveform::BLTriangle ) * 0.5f;
+				vco_k = vco_inc == 0. ? 0. : BandLimitedWave::oscillate(vco_c + 0.5f, BandLimitedWave::pdToLen(vco_inc), BandLimitedWave::Waveform::BLTriangle) * 0.5f;
 				break;
 
 			case VcoShape::BLMoog:
-				vco_k = BandLimitedWave::oscillate( vco_c + 0.5f, BandLimitedWave::pdToLen( vco_inc ), BandLimitedWave::Waveform::BLMoog );
+				vco_k = vco_inc == 0. ? 0. : BandLimitedWave::oscillate(vco_c + 0.5f, BandLimitedWave::pdToLen(vco_inc), BandLimitedWave::Waveform::BLMoog);
 				break;
 		}
 

plugins/Monstro/Monstro.cpp

@@ -320,8 +320,8 @@ void MonstroSynth::renderOutput( fpp_t _frames, sampleFrame * _buf  )
 	float rightph;
 	float pd_l;
 	float pd_r;
-	float len_l;
-	float len_r;
+	float len_l(0.);
+	float len_r(0.);
 
 	// osc1 vars
 	float o1l_f;
@@ -503,12 +503,27 @@ void MonstroSynth::renderOutput( fpp_t _frames, sampleFrame * _buf  )
 		if( pd_r > 0.5 ) pd_r = 1.0 - pd_r;
 
 		// multi-wave DC Oscillator
-		len_l = BandLimitedWave::pdToLen( pd_l );
-		len_r = BandLimitedWave::pdToLen( pd_r );
-		if( m_counter2l > 0 ) { len_l /= m_counter2l; m_counter2l--; }
-		if( m_counter2r > 0 ) { len_r /= m_counter2r; m_counter2r--; }
-		sample_t O2L = oscillate( o2w, leftph, len_l );
-		sample_t O2R = oscillate( o2w, rightph, len_r );
+		sample_t O2L = 0.;
+		if (pd_l != 0.)
+		{
+			len_l = BandLimitedWave::pdToLen(pd_l);
+			if (m_counter2l > 0)
+			{
+				len_l /= m_counter2l; m_counter2l--;
+			}
+			O2L = oscillate(o2w, leftph, len_l);
+		}
+
+		sample_t O2R = 0.;
+		if (len_r != 0.)
+		{
+			len_r = BandLimitedWave::pdToLen(pd_r);
+			if (m_counter2r > 0)
+			{
+				len_r /= m_counter2r; m_counter2r--;
+			}
+			O2R = oscillate(o2w, rightph, len_r);
+		}
 
 		// modulate volume
 		O2L *= o2lv;
@@ -568,17 +583,40 @@ void MonstroSynth::renderOutput( fpp_t _frames, sampleFrame * _buf  )
 		if( pd_r > 0.5 ) pd_r = 1.0 - pd_r;
 
 		// multi-wave DC Oscillator
-		len_l = BandLimitedWave::pdToLen( pd_l );
-		len_r = BandLimitedWave::pdToLen( pd_r );
-		if( m_counter3l > 0 ) { len_l /= m_counter3l; m_counter3l--; }
-		if( m_counter3r > 0 ) { len_r /= m_counter3r; m_counter3r--; }
-		//  sub-osc 1
-		sample_t O3AL = oscillate( o3w1, leftph, len_l );
-		sample_t O3AR = oscillate( o3w1, rightph, len_r );
+		sample_t O3AL = 0.;
+		sample_t O3AR = 0.;
 
 		// multi-wave DC Oscillator, sub-osc 2
-		sample_t O3BL = oscillate( o3w2, leftph, len_l );
-		sample_t O3BR = oscillate( o3w2, rightph, len_r );
+		sample_t O3BL = 0.;
+		sample_t O3BR = 0.;
+
+		if (pd_l != 0.)
+		{
+			len_l = BandLimitedWave::pdToLen(pd_l);
+			if (m_counter3l > 0)
+			{
+				len_l /= m_counter3l; m_counter3l--;
+			}
+			//  sub-osc 1
+			O3AL = oscillate(o3w1, leftph, len_l);
+
+			// multi-wave DC Oscillator, sub-osc 2
+			O3BL = oscillate(o3w2, leftph, len_l);
+		}
+
+		if (pd_r != 0.)
+		{
+			len_r = BandLimitedWave::pdToLen(pd_r);
+			if (m_counter3r > 0)
+			{
+				len_r /= m_counter3r; m_counter3r--;
+			}
+			//  sub-osc 1
+			O3AR = oscillate(o3w1, rightph, len_r);
+
+			// multi-wave DC Oscillator, sub-osc 2
+			O3BR = oscillate(o3w2, rightph, len_r);
+		}
 
 		// calc and modulate sub
 		sub = o3sub;