| Summary: | "double free or corruption" error appeares while i try to draw dotted line | ||
|---|---|---|---|
| Product: | cairo | Reporter: | Sergey Pevzner <pserg.sema> |
| Component: | general | Assignee: | Chris Wilson <chris> |
| Status: | RESOLVED MOVED | QA Contact: | cairo-bugs mailing list <cairo-bugs> |
| Severity: | normal | ||
| Priority: | medium | CC: | pserg.sema |
| Version: | 1.12.16 | ||
| Hardware: | x86-64 (AMD64) | ||
| OS: | Linux (All) | ||
| Whiteboard: | |||
| i915 platform: | i915 features: | ||
| Bug Depends on: | |||
| Bug Blocks: | 68382 | ||
| Attachments: |
Patch adding two printfs calls highlighting the cause for the heap corruption
testcase |
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Created attachment 95052 [details] [review] Patch adding two printfs calls highlighting the cause for the heap corruption With the attached patch and running the test program under valgrind, we get the following output: converter->spans allocated array of size 71 Using index 71 ==15967== Invalid write of size 4 ==15967== at 0x4ED51E6: _cairo_tor22_scan_converter_generate (cairo-tor22-scan-converter.c:1443) ==15967== by 0x4EC14BF: clip_and_composite_polygon (cairo-spans-compositor.c:801) ==15967== by 0x4EC2106: _cairo_spans_compositor_stroke (cairo-spans-compositor.c:1083) ==15967== by 0x4E61EFB: _cairo_compositor_stroke.part.0 (cairo-compositor.c:157) [...] ==15967== Address 0x8333638 is 0 bytes after a block of size 568 alloc'd [...] index used So the tor22 scan converter reads one entry behind the converter's spans array. Figuring out why this happens, turning this into a unit test for the test suite and checking if the other scan converters are affected, too, is left as an excercise for someone who knows more about this code. Oh it's trivial. This is how far I got this morning: commit f620c1b24ba9a80518da22c579ada65582885c82 Author: Chris Wilson <chris@chris-wilson.co.uk> Date: Mon Mar 3 11:43:24 2014 +0000 tor22: Fix off-by-one in allocation of spans The range [xmin, xmax] is inclusive and so requires xmax-xmin+1 slots. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75705 Testcase: Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Chris, I'm not finding your aforementioned patch anywhere; mind attaching it here? Here a possible fix that seems to be in line with the commit message above is to copy the first lines of the function 'glitter_scan_converter_reset' from the file src/cairo-tor-scan-converter.c and paste them in the file src/cairo-tor22-scan-converter.c so that their implementations match. Created attachment 112338 [details] [review] testcase Apparently none of the tests in the test-suite exercises tor22 scan converter, at least for the image backend. Forcing CAIRO_ANTIALIAS_FAST and tolerance=1 to the context before running the tests shows many tests would use tor22 scan converter, but no test crashes This means that it is easier to add a new test based on the bug report than to adapt an existing one. If you need a small image it is sufficient the horizontal stroke, I've attached a patch as an example. It is missing the license and copyright notice to let Sergey choose it and receive the credit. The output is deliberately black on black, easy to get right for all backends. BTW, according to grep, there is only another function named glitter_scan_converter_reset (in src/cairo-clip-tor-scan-converter.c), but it has a different signature and implementation: bugs there would not be related to this report. -- GitLab Migration Automatic Message -- This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity. You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/cairo/cairo/issues/44. |
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/* "double free or corruption" error appeares while i try to draw dotted line in case I comment line: cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND); or change antialias type to CAIRO_ANTIALIAS_BEST - all work properly */ #include<cstdio> #include<cairo/cairo.h> int main() { cairo_surface_t *surface; cairo_t *cr; surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 256, 256); cr = cairo_create(surface); cairo_set_source_rgba(cr, 0, 0, 0, 1); cairo_paint(cr); cairo_set_line_cap(cr, CAIRO_LINE_CAP_ROUND); cairo_set_line_join(cr, CAIRO_LINE_JOIN_ROUND); cairo_new_path(cr); cairo_move_to(cr, 100, 251); cairo_line_to(cr, 100, 196); cairo_move_to(cr, 36, 3); cairo_line_to(cr, 107, 3); cairo_set_antialias(cr, CAIRO_ANTIALIAS_FAST); cairo_set_tolerance(cr, 1); double dsh[2] = {1,3}; cairo_set_dash(cr, dsh, 2, 0); cairo_set_source_rgba(cr, 1, 1, 1, 1); cairo_set_line_width(cr, 2); cairo_stroke(cr); cairo_destroy (cr); cairo_surface_write_to_png (surface, "hello.png"); cairo_surface_destroy (surface); return 0; }