AudioAlsa/AudioOss: set FD_CLOEXEC flag for file descriptors

Per default child processes inherit all file descriptors of their
parent process. This applied for file descriptors pointing to sound
devices as well. Reopening sound devices while e.g. a ZynAddSubFX
process was running always failed due to this "feature".

By manually setting the FD_CLOEXEC flag for the sound device file
descriptors they do not get inherited by child processes anymore.
(cherry picked from commit 80f101cec6)

src/core/audio/AudioAlsa.cpp

@@ -46,9 +46,9 @@ AudioAlsa::AudioAlsa( bool & _success_ful, mixer * _mixer ) :
 	m_handle( NULL ),
 	m_hwParams( NULL ),
 	m_swParams( NULL ),
-	m_convertEndian( FALSE )
+	m_convertEndian( false )
 {
-	_success_ful = FALSE;
+	_success_ful = false;
 
 	int err;
 
@@ -78,7 +78,22 @@ AudioAlsa::AudioAlsa( bool & _success_ful, mixer * _mixer ) :
 		return;
 	}
 
-	_success_ful = TRUE;
+	// set FD_CLOEXEC flag for all file descriptors so forked processes
+	// do not inherit them
+	struct pollfd * ufds;
+	int count = snd_pcm_poll_descriptors_count( m_handle );
+	ufds = new pollfd[count];
+	snd_pcm_poll_descriptors( m_handle, ufds, count );
+	for( int i = 0; i < qMax( 3, count ); ++i )
+	{
+		const int fd = ( i >= count ) ? ufds[0].fd+i : ufds[i].fd;
+		int oldflags = fcntl( fd, F_GETFD, 0 );
+		if( oldflags < 0 )
+			continue;
+		oldflags |= FD_CLOEXEC;
+		fcntl( fd, F_SETFD, oldflags );
+	}
+	_success_ful = true;
 }
 
 
@@ -236,8 +251,8 @@ void AudioAlsa::run()
 	int outbuf_pos = 0;
 	int pcmbuf_size = m_periodSize * channels();
 
-	bool quit = FALSE;
-	while( quit == FALSE )
+	bool quit = false;
+	while( quit == false )
 	{
 		int_sample_t * ptr = pcmbuf;
 		int len = pcmbuf_size;
@@ -249,7 +264,7 @@ void AudioAlsa::run()
 				const fpp_t frames = getNextBuffer( temp );
 				if( !frames )
 				{
-					quit = TRUE;
+					quit = true;
 					memset( ptr, 0, len
 						* sizeof( int_sample_t ) );
 					break;

src/core/audio/AudioOss.cpp

@@ -97,6 +97,10 @@ AudioOss::AudioOss( bool & _success_ful, mixer * _mixer ) :
 		return;
 	}
 
+	// set FD_CLOEXEC flag for file descriptor so forked processes
+	// do not inherit it
+	fcntl( m_audioFD, F_SETFD, fcntl( m_audioFD, F_GETFD ) | FD_CLOEXEC );
+
 	int frag_spec;
 	for( frag_spec = 0; static_cast<int>( 0x01 << frag_spec ) <
 		getMixer()->framesPerPeriod() * channels() *