I can get everything to compile with the -prof flag now, but I get those two linking errors that I don't understand: c:/ghc/ghc-6.2.1/libHSGLUT_p.a(Debugging.p_o)(.text+0x748):Debugging.p_hc: undefined reference to `GraphicsziRenderingziOpenGLziGLUziErrors_getErrors_closure' c:/ghc/ghc-6.2.1/libHSGLUT_p.a(Debugging.p_o)(.text+0x7a4):Debugging.p_hc: undefined reference to `GraphicsziRenderingziOpenGLziGLUziErrors_getErrors_entry' make: *** [renderer] Error 1 My configuration is a bit weird: I compile HOpenGL and GLUT from a 6.3 fptools distribution, but I install the resulting packages in a 6.2.1 binary distribution (because for some reason I don't remember I was having trouble building the whole fptools 6.3). I'm using cygwin on a win XP PC. In case it's relevent, the package.conf entries for GLUT and OpenGL read like this: Package {name = "OpenGL", auto = True, import_dirs = ["$libdir/imports"], source_dirs = [], library_dirs = ["$libdir"], hs_libraries = ["HSOpenGL"], extra_libraries = ["HSOpenGL_cbits"], include_dirs = [], c_includes = ["HsOpenGL.h"], package_deps = ["base"], extra_ghc_opts = [], extra_cc_opts = [], extra_ld_opts = ["-lglu32", "-lopengl32"], framework_dirs = [], extra_frameworks = []}, Package {name = "GLUT", auto = True, import_dirs = ["$libdir/imports"], source_dirs = [], library_dirs = ["$libdir"], hs_libraries = ["HSGLUT"], extra_libraries = ["HSGLUT_cbits"], include_dirs = [], c_includes = ["HsGLUT.h"], package_deps = ["base", "OpenGL"], extra_ghc_opts = [], extra_cc_opts = [], extra_ld_opts = ["-lglut32"], framework_dirs = [], extra_frameworks = []}, Thank you for your help, Yann Morvan