use nullptr for all null pointer constants

Also add `-Wzero-as-null-pointer-constant` to cxx flags.

CMakeLists.txt

@@ -6,10 +6,18 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/cmake")
 
 include(CMakePushCheckState)
 include(CheckCXXSourceCompiles)
+include(CheckCXXCompilerFlag)
 include(TestBigEndian)
 include(GNUInstallDirs)
 include(CTest)
 
+macro(gme_add_cxx_warning_flag WARNINGFLAG WARNING_VAR)
+    check_cxx_compiler_flag("-W${WARNINGFLAG}" HAVE_CXXW_${WARNING_VAR})
+    if(HAVE_CXXW_${WARNING_VAR})
+        set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -W${WARNINGFLAG}")
+    endif()
+endmacro()
+
 file(READ "gme/gme.h" GME_GME_H)
 string(REGEX MATCH "/\\* Game_Music_Emu ([0-9]+)\\.([0-9]+).([0-9]+) \\*/" RE_GME_VERSION "${GME_GME_H}")
 if(NOT RE_GME_VERSION)
@@ -64,13 +72,16 @@ elseif(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
 endif()
 
 # Check for GCC/Clang "visibility" support.
-if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang" AND ENABLE_UBSAN)
+if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
+  gme_add_cxx_warning_flag(zero-as-null-pointer-constant ZERO_AS_NULLPTR_CONSTANT)
+  if(ENABLE_UBSAN)
     # GCC needs -static-libubsan
     if(NOT BUILD_SHARED_LIBS AND CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=undefined -static-libubsan")
     else()
         set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=undefined")
     endif()
+  endif()
 endif()
 
 # Shared library defined here

demo/Wave_Writer.cpp

@@ -44,7 +44,7 @@ Wave_Writer::Wave_Writer( long sample_rate, const char* filename )
 	if ( !file )
 		exit_with_error( "Couldn't open WAVE file for writing" );
 
-	setvbuf( file, 0, _IOFBF, 32 * 1024L );
+	setvbuf( file, nullptr, _IOFBF, 32 * 1024L );
 }
 
 void Wave_Writer::flush()
@@ -151,7 +151,7 @@ void Wave_Writer::close()
 		fwrite( header, sizeof header, 1, file );
 
 		fclose( file );
-		file = 0;
+		file = nullptr;
 		free( buf );
 	}
 }
@@ -180,5 +180,5 @@ void wave_write( const short* buf, long count ) { ww->write( buf, count ); }
 void wave_close()
 {
 	delete ww;
-	ww = 0;
+	ww = nullptr;
 }

gme/Ay_Apu.cpp

@@ -89,7 +89,7 @@ Ay_Apu::Ay_Apu()
 		}
 	}
 
-	output( 0 );
+	output( nullptr );
 	volume( 1.0 );
 	reset();
 }

gme/Ay_Emu.cpp

@@ -31,7 +31,7 @@ using std::max;
 
 Ay_Emu::Ay_Emu()
 {
-	beeper_output = 0;
+	beeper_output = nullptr;
 	set_type( gme_ay_type );
 
 	static const char* const names [osc_count] = {
@@ -57,7 +57,7 @@ static byte const* get_data( Ay_Emu::file_t const& file, byte const* ptr, int mi
 	assert( (unsigned long) pos <= (unsigned long) file_size - 2 );
 	int offset = (int16_t) get_be16( ptr );
 	if ( !offset || blargg_ulong (pos + offset) > blargg_ulong (file_size - min_size) )
-		return 0;
+		return nullptr;
 	return ptr + offset;
 }
 
@@ -78,7 +78,7 @@ static blargg_err_t parse_header( byte const* in, long size, Ay_Emu::file_t* out
 	if ( !out->tracks )
 		return "Missing track data";
 
-	return 0;
+	return nullptr;
 }
 
 static void copy_ay_fields( Ay_Emu::file_t const& file, track_info_t* out, int track )
@@ -95,7 +95,7 @@ static void copy_ay_fields( Ay_Emu::file_t const& file, track_info_t* out, int t
 blargg_err_t Ay_Emu::track_info_( track_info_t* out, int track ) const
 {
 	copy_ay_fields( file, out, track );
-	return 0;
+	return nullptr;
 }
 
 struct Ay_File : Gme_Info_
@@ -108,13 +108,13 @@ struct Ay_File : Gme_Info_
 	{
 		RETURN_ERR( parse_header( begin, size, &file ) );
 		set_track_count( file.header->max_track + 1 );
-		return 0;
+		return nullptr;
 	}
 
 	blargg_err_t track_info_( track_info_t* out, int track ) const
 	{
 		copy_ay_fields( file, out, track );
-		return 0;
+		return nullptr;
 	}
 };
 
@@ -274,7 +274,7 @@ blargg_err_t Ay_Emu::start_track_( int track )
 	cpc_mode      = false;
 	cpc_latch     = 0;
 
-	return 0;
+	return nullptr;
 }
 
 // Emulation
@@ -406,5 +406,5 @@ blargg_err_t Ay_Emu::run_clocks( blip_time_t& duration, int )
 
 	apu.end_frame( duration );
 
-	return 0;
+	return nullptr;
 }

gme/Blip_Buffer.cpp

@@ -29,7 +29,7 @@ Blip_Buffer::Blip_Buffer()
 {
 	factor_       = (blip_ulong)-1 / 2;
 	offset_       = 0;
-	buffer_       = 0;
+	buffer_       = nullptr;
 	buffer_size_  = 0;
 	sample_rate_  = 0;
 	reader_accum_ = 0;
@@ -117,7 +117,7 @@ Blip_Buffer::blargg_err_t Blip_Buffer::set_sample_rate( long new_rate, int msec
 
 	clear();
 
-	return 0; // success
+	return nullptr; // success
 }
 
 blip_resampled_time_t Blip_Buffer::clock_rate_factor( long rate ) const
@@ -191,7 +191,7 @@ void Blip_Buffer::remove_samples( long count )
 
 Blip_Synth_Fast_::Blip_Synth_Fast_()
 {
-	buf = 0;
+	buf = nullptr;
 	last_amp = 0;
 	delta_factor = 0;
 }
@@ -209,7 +209,7 @@ Blip_Synth_::Blip_Synth_( short* p, int w ) :
 {
 	volume_unit_ = 0.0;
 	kernel_unit = 0;
-	buf = 0;
+	buf = nullptr;
 	last_amp = 0;
 	delta_factor = 0;
 }

gme/Classic_Emu.cpp

@@ -20,9 +20,9 @@ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
 
 Classic_Emu::Classic_Emu()
 {
-	buf           = 0;
-	stereo_buffer = 0;
-	voice_types   = 0;
+	buf           = nullptr;
+	stereo_buffer = nullptr;
+	voice_types   = nullptr;
 
 	// avoid inconsistency in our duplicated constants
 	blaarg_static_assert( (int) wave_type  == (int) Multi_Buffer::wave_type, "wave_type inconsistent across two classes using it" );
@@ -57,7 +57,7 @@ blargg_err_t Classic_Emu::set_sample_rate_( long rate )
 blargg_err_t Classic_Emu::set_multi_channel ( bool is_enabled )
 {
         RETURN_ERR( Music_Emu::set_multi_channel_( is_enabled ) );
-        return 0;
+        return nullptr;
 }
 
 void Classic_Emu::mute_voices_( int mask )
@@ -67,7 +67,7 @@ void Classic_Emu::mute_voices_( int mask )
 	{
 		if ( mask & (1 << i) )
 		{
-			set_voice( i, 0, 0, 0 );
+			set_voice( i, nullptr, nullptr, nullptr );
 		}
 		else
 		{
@@ -91,14 +91,14 @@ blargg_err_t Classic_Emu::setup_buffer( long rate )
 	RETURN_ERR( buf->set_channel_count( voice_count() ) );
 	set_equalizer( equalizer() );
 	buf_changed_count = buf->channels_changed_count();
-	return 0;
+	return nullptr;
 }
 
 blargg_err_t Classic_Emu::start_track_( int track )
 {
 	RETURN_ERR( Music_Emu::start_track_( track ) );
 	buf->clear();
-	return 0;
+	return nullptr;
 }
 
 blargg_err_t Classic_Emu::play_( long count, sample_t* out )
@@ -121,7 +121,7 @@ blargg_err_t Classic_Emu::play_( long count, sample_t* out )
 			buf->end_frame( clocks_emulated );
 		}
 	}
-	return 0;
+	return nullptr;
 }
 
 // Rom_Data
@@ -154,7 +154,7 @@ blargg_err_t Rom_Data_::load_rom_data_( Data_Reader& in,
 	memset( rom.begin()         , fill, pad_size );
 	memset( rom.end() - pad_size, fill, pad_size );
 
-	return 0;
+	return nullptr;
 }
 
 void Rom_Data_::set_addr_( long addr, int unit )

gme/Data_Reader.cpp

@@ -49,7 +49,7 @@ blargg_err_t Data_Reader::read( void* p, long s )
 		return "Read error";
 	}
 
-	return 0;
+	return nullptr;
 }
 
 blargg_err_t Data_Reader::skip( long count )
@@ -65,7 +65,7 @@ blargg_err_t Data_Reader::skip( long count )
 		count -= n;
 		RETURN_ERR( read( buf, n ) );
 	}
-	return 0;
+	return nullptr;
 }
 
 long File_Reader::remain() const { return size() - tell(); }
@@ -75,7 +75,7 @@ blargg_err_t File_Reader::skip( long n )
 	RETURN_VALIDITY_CHECK( n >= 0 );
 
 	if ( !n )
-		return 0;
+		return nullptr;
 	return seek( tell() + n );
 }
 
@@ -146,7 +146,7 @@ blargg_err_t Remaining_Reader::read( void* out, long count )
 	long first = read_first( out, count );
 	long second = max( 0l, count - first );
 	if ( !second )
-		return 0;
+		return nullptr;
 	return in->read( (char*) out + first, second );
 }
 
@@ -197,7 +197,7 @@ blargg_err_t Mem_File_Reader::seek( long n )
 	if ( n > m_size )
 		return eof_error;
 	m_pos = n;
-	return 0;
+	return nullptr;
 }
 
 #ifdef HAVE_ZLIB_H
@@ -224,8 +224,8 @@ bool Mem_File_Reader::gz_decompress()
 	strm.next_in   = const_cast<Bytef *>( reinterpret_cast<const Bytef *>( m_begin ) );
 	strm.avail_in  = static_cast<uInt>( m_size );
 	strm.total_out = 0;
-	strm.zalloc    = Z_NULL;
-	strm.zfree     = Z_NULL;
+	strm.zalloc    = nullptr;
+	strm.zfree     = nullptr;
 
 	bool done = false;
 
@@ -404,7 +404,7 @@ blargg_err_t Std_File_Reader::read( void* p, long s )
 #endif
 	const auto &file = reinterpret_cast<FILE*>( file_ );
 	if ( s == static_cast<long>( fread( p, 1, static_cast<size_t>(s), file ) ) )
-		return 0;
+		return nullptr;
 	if ( feof( file ) )
 		return eof_error;
 	return "Couldn't read from file";

gme/Data_Reader.h

@@ -135,7 +135,7 @@ class Remaining_Reader : public Data_Reader {
 class Callback_Reader : public Data_Reader {
 public:
 	typedef const char* (*callback_t)( void* data, void* out, int count );
-	Callback_Reader( callback_t, long size, void* data = 0 );
+	Callback_Reader( callback_t, long size, void* data = nullptr );
 public:
 	long read_avail( void*, long );
 	blargg_err_t read( void*, long );

gme/Fir_Resampler.cpp

@@ -57,7 +57,7 @@ Fir_Resampler_::Fir_Resampler_( int width, sample_t* impulses_ ) :
 	write_offset( width * stereo - stereo ),
 	impulses( impulses_ )
 {
-	write_pos = 0;
+	write_pos = nullptr;
 	res       = 1;
 	imp_phase = 0;
 	skip_bits = 0;
@@ -81,7 +81,7 @@ blargg_err_t Fir_Resampler_::buffer_size( int new_size )
 {
 	RETURN_ERR( buf.resize( new_size + write_offset ) );
 	clear();
-	return 0;
+	return nullptr;
 }
 
 double Fir_Resampler_::time_ratio( double new_factor, double rolloff, double gain )

gme/Gb_Apu.cpp

@@ -42,11 +42,11 @@ Gb_Apu::Gb_Apu()
 	{
 		Gb_Osc& osc = *oscs [i];
 		osc.regs = &regs [i * 5];
-		osc.output = 0;
-		osc.outputs [0] = 0;
-		osc.outputs [1] = 0;
-		osc.outputs [2] = 0;
-		osc.outputs [3] = 0;
+		osc.output = nullptr;
+		osc.outputs [0] = nullptr;
+		osc.outputs [1] = nullptr;
+		osc.outputs [2] = nullptr;
+		osc.outputs [3] = nullptr;
 	}
 
 	set_tempo( 1.0 );

gme/Gb_Cpu.h

@@ -14,7 +14,7 @@ class Gb_Cpu {
 	enum { clocks_per_instr = 4 };
 public:
 	// Clear registers and map all pages to unmapped
-	void reset( void* unmapped = 0 );
+	void reset( void* unmapped = nullptr );
 
 	// Map code memory (memory accessed via the program counter). Start and size
 	// must be multiple of page_size.