This is what I get after including the pixman 0.34 symbols. Most of the Uninitialised value errors are gone. Only a few remain. I should probably update to Ubuntu18.04 next and stay a little more current. Eric ==24063== Memcheck, a memory error detector ==24063== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al. ==24063== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info ==24063== Command: ./cairo_test2 ==24063== Cairo Version 1.15.10 ==24063== Conditional jump or move depends on uninitialised value(s) ==24063== at 0x4610AAE: core_combine_over_u_sse2_mask (pixman-sse2.c:587) ==24063== by 0x4610AAE: sse2_combine_over_u (pixman-sse2.c:738) ==24063== by 0x4588D25: general_composite_rect (pixman-general.c:223) ==24063== by 0x43DA4EA: pixman_image_composite32 (pixman.c:700) ==24063== by 0x406BFB9: _inplace_spans (cairo-image-compositor.c:2520) ==24063== by 0x40BA70F: blit_a1 (cairo-tor-scan-converter.c:1712) ==24063== by 0x40BA70F: glitter_scan_converter_render (cairo-tor-scan-converter.c:1797) ==24063== by 0x40BA70F: _cairo_tor_scan_converter_generate (cairo-tor-scan-converter.c:1857) ==24063== by 0x40AA97D: composite_polygon.isra.8 (cairo-spans-compositor.c:801) ==24063== by 0x40AB4CE: clip_and_composite_polygon (cairo-spans-compositor.c:967) ==24063== by 0x40AC071: _cairo_spans_compositor_stroke (cairo-spans-compositor.c:1083) ==24063== by 0x405D746: _cairo_compositor_stroke (cairo-compositor.c:157) ==24063== by 0x40717CA: _cairo_image_surface_stroke (cairo-image-surface.c:966) ==24063== by 0x40B048A: _cairo_surface_stroke (cairo-surface.c:2377) ==24063== by 0x4067221: _cairo_gstate_stroke (cairo-gstate.c:1188) ==24063== Uninitialised value was created by a stack allocation ==24063== at 0x4588832: general_composite_rect (pixman-general.c:129) ==24063== ==24063== Conditional jump or move depends on uninitialised value(s) ==24063== at 0x4611B7A: core_combine_over_u_sse2_mask (pixman-sse2.c:649) ==24063== by 0x4611B7A: sse2_combine_over_u (pixman-sse2.c:738) ==24063== by 0x4588D25: general_composite_rect (pixman-general.c:223) ==24063== by 0x43DA4EA: pixman_image_composite32 (pixman.c:700) ==24063== by 0x406BFB9: _inplace_spans (cairo-image-compositor.c:2520) ==24063== by 0x40BA70F: blit_a1 (cairo-tor-scan-converter.c:1712) ==24063== by 0x40BA70F: glitter_scan_converter_render (cairo-tor-scan-converter.c:1797) ==24063== by 0x40BA70F: _cairo_tor_scan_converter_generate (cairo-tor-scan-converter.c:1857) ==24063== by 0x40AA97D: composite_polygon.isra.8 (cairo-spans-compositor.c:801) ==24063== by 0x40AB4CE: clip_and_composite_polygon (cairo-spans-compositor.c:967) ==24063== by 0x40AC071: _cairo_spans_compositor_stroke (cairo-spans-compositor.c:1083) ==24063== by 0x405D746: _cairo_compositor_stroke (cairo-compositor.c:157) ==24063== by 0x40717CA: _cairo_image_surface_stroke (cairo-image-surface.c:966) ==24063== by 0x40B048A: _cairo_surface_stroke (cairo-surface.c:2377) ==24063== by 0x4067221: _cairo_gstate_stroke (cairo-gstate.c:1188) ==24063== Uninitialised value was created by a stack allocation ==24063== at 0x4588832: general_composite_rect (pixman-general.c:129) ==24063== ==24063== Uninitialised byte(s) found during client check request ==24063== at 0x405ED8E: _cairo_debug_check_image_surface_is_defined (cairo-debug.c:139) ==24063== by 0x40AFDDD: _cairo_surface_acquire_source_image (cairo-surface.c:2059) ==24063== by 0x40F89DD: write_png (cairo-png.c:194) ==24063== by 0x40F9525: cairo_surface_write_to_png (cairo-png.c:391) ==24063== by 0x8048F41: main (cairo_test2.c:59) ==24063== Address 0x4a9ad9c is 176,964 bytes inside a block of size 640,000 alloc'd ==24063== at 0x402E0B8: calloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==24063== by 0x45141E1: create_bits (pixman-bits-image.c:935) ==24063== by 0x4514253: _pixman_bits_image_init (pixman-bits-image.c:955) ==24063== by 0x4514419: create_bits_image_internal (pixman-bits-image.c:1005) ==24063== by 0x4514466: pixman_image_create_bits (pixman-bits-image.c:1024) ==24063== by 0x4072021: _cairo_image_surface_create_with_pixman_format (cairo-image-surface.c:349) ==24063== by 0x407228C: cairo_image_surface_create (cairo-image-surface.c:401) ==24063== by 0x8048BD9: main (cairo_test2.c:28) ==24063== Uninitialised value was created by a stack allocation ==24063== at 0x4588832: general_composite_rect (pixman-general.c:129) ==24063== Status 0 ==24063== ==24063== HEAP SUMMARY: ==24063== in use at exit: 6,192 bytes in 6 blocks ==24063== total heap usage: 108 allocs, 102 frees, 1,047,518 bytes allocated ==24063== ==24063== 1,032 bytes in 1 blocks are still reachable in loss record 1 of 6 ==24063== at 0x402C17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==24063== by 0x458A9CD: _pixman_implementation_create (pixman-implementation.c:38) ==24063== by 0x4588E11: _pixman_implementation_create_general (pixman-general.c:248) ==24063== by 0x458B11D: _pixman_choose_implementation (pixman-implementation.c:393) ==24063== by 0x43D92F6: pixman_constructor (pixman.c:39) ==24063== by 0x400F464: call_init.part.0 (dl-init.c:72) ==24063== by 0x400F58D: call_init (dl-init.c:30) ==24063== by 0x400F58D: _dl_init (dl-init.c:120) ==24063== by 0x4000A5E: ??? (in /lib/i386-linux-gnu/ld-2.23.so) ==24063== ==24063== 1,032 bytes in 1 blocks are still reachable in loss record 2 of 6 ==24063== at 0x402C17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==24063== by 0x458A9CD: _pixman_implementation_create (pixman-implementation.c:38) ==24063== by 0x45872F2: _pixman_implementation_create_fast_path (pixman-fast-path.c:3288) ==24063== by 0x458B141: _pixman_choose_implementation (pixman-implementation.c:396) ==24063== by 0x43D92F6: pixman_constructor (pixman.c:39) ==24063== by 0x400F464: call_init.part.0 (dl-init.c:72) ==24063== by 0x400F58D: call_init (dl-init.c:30) ==24063== by 0x400F58D: _dl_init (dl-init.c:120) ==24063== by 0x4000A5E: ??? (in /lib/i386-linux-gnu/ld-2.23.so) ==24063== ==24063== 1,032 bytes in 1 blocks are still reachable in loss record 3 of 6 ==24063== at 0x402C17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==24063== by 0x458A9CD: _pixman_implementation_create (pixman-implementation.c:38) ==24063== by 0x46105ED: _pixman_implementation_create_mmx (pixman-mmx.c:4115) ==24063== by 0x454BB81: _pixman_x86_get_implementations (pixman-x86.c:234) ==24063== by 0x458B152: _pixman_choose_implementation (pixman-implementation.c:398) ==24063== by 0x43D92F6: pixman_constructor (pixman.c:39) ==24063== by 0x400F464: call_init.part.0 (dl-init.c:72) ==24063== by 0x400F58D: call_init (dl-init.c:30) ==24063== by 0x400F58D: _dl_init (dl-init.c:120) ==24063== by 0x4000A5E: ??? (in /lib/i386-linux-gnu/ld-2.23.so) ==24063== ==24063== 1,032 bytes in 1 blocks are still reachable in loss record 4 of 6 ==24063== at 0x402C17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==24063== by 0x458A9CD: _pixman_implementation_create (pixman-implementation.c:38) ==24063== by 0x471D5F6: _pixman_implementation_create_sse2 (pixman-sse2.c:6471) ==24063== by 0x454BBB9: _pixman_x86_get_implementations (pixman-x86.c:239) ==24063== by 0x458B152: _pixman_choose_implementation (pixman-implementation.c:398) ==24063== by 0x43D92F6: pixman_constructor (pixman.c:39) ==24063== by 0x400F464: call_init.part.0 (dl-init.c:72) ==24063== by 0x400F58D: call_init (dl-init.c:30) ==24063== by 0x400F58D: _dl_init (dl-init.c:120) ==24063== by 0x4000A5E: ??? (in /lib/i386-linux-gnu/ld-2.23.so) ==24063== ==24063== 1,032 bytes in 1 blocks are still reachable in loss record 5 of 6 ==24063== at 0x402C17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==24063== by 0x458A9CD: _pixman_implementation_create (pixman-implementation.c:38) ==24063== by 0x471F727: _pixman_implementation_create_ssse3 (pixman-ssse3.c:345) ==24063== by 0x454BBF1: _pixman_x86_get_implementations (pixman-x86.c:244) ==24063== by 0x458B152: _pixman_choose_implementation (pixman-implementation.c:398) ==24063== by 0x43D92F6: pixman_constructor (pixman.c:39) ==24063== by 0x400F464: call_init.part.0 (dl-init.c:72) ==24063== by 0x400F58D: call_init (dl-init.c:30) ==24063== by 0x400F58D: _dl_init (dl-init.c:120) ==24063== by 0x4000A5E: ??? (in /lib/i386-linux-gnu/ld-2.23.so) ==24063== ==24063== 1,032 bytes in 1 blocks are still reachable in loss record 6 of 6 ==24063== at 0x402C17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==24063== by 0x458A9CD: _pixman_implementation_create (pixman-implementation.c:38) ==24063== by 0x458FD46: _pixman_implementation_create_noop (pixman-noop.c:155) ==24063== by 0x458B196: _pixman_choose_implementation (pixman-implementation.c:403) ==24063== by 0x43D92F6: pixman_constructor (pixman.c:39) ==24063== by 0x400F464: call_init.part.0 (dl-init.c:72) ==24063== by 0x400F58D: call_init (dl-init.c:30) ==24063== by 0x400F58D: _dl_init (dl-init.c:120) ==24063== by 0x4000A5E: ??? (in /lib/i386-linux-gnu/ld-2.23.so) ==24063== ==24063== LEAK SUMMARY: ==24063== definitely lost: 0 bytes in 0 blocks ==24063== indirectly lost: 0 bytes in 0 blocks ==24063== possibly lost: 0 bytes in 0 blocks ==24063== still reachable: 6,192 bytes in 6 blocks ==24063== suppressed: 0 bytes in 0 blocks ==24063== ==24063== For counts of detected and suppressed errors, rerun with: -v ==24063== ERROR SUMMARY: 400 errors from 3 contexts (suppressed: 0 from 0)