Fix GCC -W(maybe-)uninitialized warnings that at least kinda had a point

idlib/geometry/Surface_Patch.cpp

@@ -224,6 +224,7 @@ idSurface_Patch::LerpVert
 ============
 */
 void idSurface_Patch::LerpVert( const idDrawVert &a, const idDrawVert &b, idDrawVert &out ) const {
+	// DG: TODO: what about out.tangent and out.color ?
 	out.xyz[0] = 0.5f * ( a.xyz[0] + b.xyz[0] );
 	out.xyz[1] = 0.5f * ( a.xyz[1] + b.xyz[1] );
 	out.xyz[2] = 0.5f * ( a.xyz[2] + b.xyz[2] );
@@ -554,7 +555,11 @@ idSurface_Patch::Subdivide
 */
 void idSurface_Patch::Subdivide( float maxHorizontalError, float maxVerticalError, float maxLength, bool genNormals ) {
 	int			i, j, k, l;
-	idDrawVert	prev, next, mid;
+	// DG: to shut up GCC (maybe-)uninitialized warnings, initialize prev, next and mid
+	//     (maybe the warnings were at least partly correct, because .tangent and .color aren't set by idSurface_Patch::LerpVert())
+	idDrawVert	prev;
+	prev.Clear();
+	idDrawVert next = prev, mid = prev;
 	idVec3		prevxyz, nextxyz, midxyz;
 	idVec3		delta;
 	float		maxHorizontalErrorSqr, maxVerticalErrorSqr, maxLengthSqr;

idlib/geometry/Winding.cpp

@@ -102,7 +102,12 @@ int idWinding::Split( const idPlane &plane, const float epsilon, idWinding **fro
 	idWinding *		f, *b;
 	int				maxpts;
 
-	assert( this );
+	assert( this && numPoints > 0);
+
+	// DG: unlikely, but makes sure we don't use uninitialized memory below
+	if ( numPoints == 0 ) {
+		return 0; // it's not like the callers check the return value anyway..
+	}
 
 	dists = (float *) _alloca( (numPoints+4) * sizeof( float ) );
 	sides = (byte *) _alloca( (numPoints+4) * sizeof( byte ) );
@@ -245,7 +250,13 @@ idWinding *idWinding::Clip( const idPlane &plane, const float epsilon, const boo
 	idVec5		mid;
 	int			maxpts;
 
-	assert( this );
+	assert( this && numPoints > 0 );
+
+	// DG: this shouldn't happen, probably, but if it does we'd use uninitialized memory below
+	if ( numPoints == 0 ) {
+		delete this;
+		return NULL;
+	}
 
 	dists = (float *) _alloca( (numPoints+4) * sizeof( float ) );
 	sides = (byte *) _alloca( (numPoints+4) * sizeof( byte ) );

idlib/geometry/Winding2D.cpp

@@ -92,6 +92,12 @@ void idWinding2D::ExpandForAxialBox( const idVec2 bounds[2] ) {
 		assert( numPlanes < MAX_POINTS_ON_WINDING_2D );
 		planes[numPlanes++] = plane;
 	}
+
+	// DG: make sure planes[] isn't used uninitialized and with index -1 below
+	if ( numPlanes == 0 ) {
+		return;
+	}
+
 	if ( GetAxialBevel( planes[numPlanes-1], planes[0], p[0], bevel ) ) {
 		planes[numPlanes++] = bevel;
 	}
@@ -259,6 +265,11 @@ bool idWinding2D::ClipInPlace( const idVec3 &plane, const float epsilon, const b
 	float dot, dists[MAX_POINTS_ON_WINDING_2D+1];
 	idVec2 *p1, *p2, mid, newPoints[MAX_POINTS_ON_WINDING_2D+4];
 
+	// DG: avoid all kinds of unitialized usages below
+	if ( numPoints == 0 ) {
+		return false;
+	}
+
 	counts[SIDE_FRONT] = counts[SIDE_BACK] = counts[SIDE_ON] = 0;
 
 	for ( i = 0; i < numPoints; i++ ) {

idlib/math/Simd_SSE.cpp

@@ -456,6 +456,14 @@ void VPCALL idSIMD_SSE::Dot( float *dst, const idVec3 &constant, const idPlane *
 	char *dst_p;
 	__m128 xmm0, xmm1, xmm2, xmm3, xmm4, xmm5, xmm6, xmm7;
 
+	// DG: GCC and clang warn about xmm1-4 maybe being used uninitialized below.
+	//     according to https://stackoverflow.com/a/18749079 the initialization
+	//     code is generated anyway, so make it explicit to shut up the warning
+	xmm1 = _mm_setzero_ps();
+	xmm2 = _mm_setzero_ps();
+	xmm3 = _mm_setzero_ps();
+	xmm4 = _mm_setzero_ps();
+
 	/*
 		mov			eax, count
 		mov			edi, constant