Remove the -Wno-unused-function hider. Should be able to fix these with this method if any more crop up on Linux.

code/math/fvi.cpp

@@ -1079,6 +1079,8 @@ void fvi_closest_line_line(const vec3d *x0, const vec3d *vx, const vec3d *y0, co
 }
 
 // --------------------------------------------------------------------------------------------------------------------
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-function"
 static void accurate_square_root( float A, float B, float C, float discriminant, float *root1, float *root2 )
 {
 	float root = fl_sqrt(discriminant);
@@ -1091,6 +1093,7 @@ static void accurate_square_root( float A, float B, float C, float discriminant,
 		*root2 = 2.0f*C / (-B + root);
 	}
 }
+#pragma GCC diagnostic pop
 
 /**
  * Project point on bounding box

code/math/vecmat.cpp

@@ -1581,6 +1581,8 @@ void vm_quaternion_rotate(matrix *M, float theta, const vec3d *u)
 //		inputs:	m			=>		point to resultant rotation matrix
 //				angle		=>		rotation angle about z axis (in radians)
 //
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-function"
 static void rotate_z ( matrix *m, float theta )
 {
 	m->vec.rvec.xyz.x = cosf (theta);
@@ -1595,6 +1597,7 @@ static void rotate_z ( matrix *m, float theta )
 	m->vec.fvec.xyz.y = 0.0f;
 	m->vec.fvec.xyz.z = 1.0f;
 }
+#pragma GCC diagnostic pop
 
 
 // --------------------------------------------------------------------------------------

configure.ac

@@ -251,7 +251,7 @@ fi
 
 if test "$fs2_debug" = "yes" ; then
 	AC_DEFINE([_DEBUG])
-	D_CFLAGS="$D_CFLAGS -O0 -g -Wall -Wextra -Wno-unused-parameter -Wno-unused-function -Wno-write-strings -Wshadow -funroll-loops"
+	D_CFLAGS="$D_CFLAGS -O0 -g -Wall -Wextra -Wno-unused-parameter -Wno-write-strings -Wshadow -funroll-loops"
 	D_LDFLAGS="$D_LDFLAGS -g"
 
 	if test "$fs2_fred" = "yes" ; then
@@ -262,7 +262,7 @@ if test "$fs2_debug" = "yes" ; then
 else
 	AC_DEFINE([NDEBUG])
 	D_CFLAGS="$D_CFLAGS -O2 -Wall -funroll-loops"
-	D_CFLAGS="$D_CFLAGS -Wno-unused-function -Wno-write-strings -Wno-unused-variable"
+	D_CFLAGS="$D_CFLAGS -Wno-write-strings -Wno-unused-variable"
 	
 	AC_C_COMPILE_FLAGS([-Wno-unused-but-set-variable])