Without this I've got:
```
src/engine/enginefiltereffect.cpp: In member function 'virtual void EngineFilterEffect::process(const CSAMPLE*, const CSAMPLE*, int)':
src/engine/enginefiltereffect.cpp:62:69: error: invalid conversion from 'const CSAMPLE* {aka const float*}' to 'CSAMPLE* {aka float*}' [-fpermissive]
In file included from src/engine/enginefiltereffect.cpp:3:0:
src/sampleutil.h:82:17: error:   initializing argument 1 of 'static void SampleUtil::copyWithGain(CSAMPLE*, const CSAMPLE*, CSAMPLE, int)' [-fpermissive]
src/engine/enginefiltereffect.cpp:68:69: error: invalid conversion from 'const CSAMPLE* {aka const float*}' to 'CSAMPLE* {aka float*}' [-fpermissive]
In file included from src/engine/enginefiltereffect.cpp:3:0:
src/sampleutil.h:82:17: error:   initializing argument 1 of 'static void SampleUtil::copyWithGain(CSAMPLE*, const CSAMPLE*, CSAMPLE, int)' [-fpermissive]
src/engine/enginefiltereffect.cpp:72:69: error: invalid conversion from 'const CSAMPLE* {aka const float*}' to 'CSAMPLE* {aka float*}' [-fpermissive]
In file included from src/engine/enginefiltereffect.cpp:3:0:
src/sampleutil.h:82:17: error:   initializing argument 1 of 'static void SampleUtil::copyWithGain(CSAMPLE*, const CSAMPLE*, CSAMPLE, int)' [-fpermissive]
src/engine/enginefiltereffect.cpp:106:40: error: invalid conversion from 'const CSAMPLE* {aka const float*}' to 'CSAMPLE* {aka float*}' [-fpermissive]
src/engine/enginefiltereffect.cpp:35:6: error:   initializing argument 2 of 'void EngineFilterEffect::applyFilters(const CSAMPLE*, CSAMPLE*, int)' [-fpermissive]
src/engine/enginefiltereffect.cpp:111:61: error: invalid conversion from 'const CSAMPLE* {aka const float*}' to 'CSAMPLE* {aka float*}' [-fpermissive]
In file included from src/engine/enginefiltereffect.cpp:3:0:
src/sampleutil.h:131:17: error:   initializing argument 1 of 'static void SampleUtil::linearCrossfadeBuffers(CSAMPLE*, const CSAMPLE*, const CSAMPLE*, int)' [-fpermissive]
```