[cairo] User code triggers some inner Cairo assert

Jonas Kulla nyocurio at gmail.com
Fri Sep 14 09:17:19 PDT 2012

2012/9/14 Sebastien Kramm <sebastien.kramm at univ-rouen.fr>

> Hello,
> This is my first post here.
> For some application, I am writing a wrapper over basic drawing stuff with
> cairo, and the corresponding images are displayed into Gtk+2 windows. It
> ""kinda works"". However, one of my samples triggers an internal cairo
> assert, and I really don't see how to fix this. The log is:
> demo1: /build/buildd/cairo-1.10.2/**src/cairo.c:173: _cairo_error:
> Assertion `(status != CAIRO_STATUS_SUCCESS && status <=
> Something in my code is probably doing something really bad, but I don't
> know what.
> FIY, its a C++ app, that is calling a set of C functions that are wrappers
> over the drawing back-end library (Cairo) and window managment (Gtk+2).
> I only use a small subset of the Cairo functions, drawing on images is
> done with the classical pattern (creating a cairo_t* with cairo_create(),
> drawing, then release the object).
> From error message, I seem to be using 1.10 version (plateform is Ubuntu
> 12.04). I tried to upgrade to 1.12, but the classical:
>   sudo apt-get install libcairo2-dev
> as suggested by:
>   http://www.cairographics.org/**download/<http://www.cairographics.org/download/>
> tells me that:
>   "libcairo2-dev is already the newest version"
> (although this seems to be false).
> I checked the corresponding code via:
>   http://cgit.freedesktop.org/**cairo/tree/src/cairo.c?id=1.**10.2<http://cgit.freedesktop.org/cairo/tree/src/cairo.c?id=1.10.2>
> and the assert is in some function:
>    cairo_status_t _cairo_error (cairo_status_t status)
> that my code does NOT call.
> My knowledge of Cairo is very limited, so I'm stuck. Any advice on how to
> move on would be appreciated.

Hi Sebastien,

it would really really help if you could provide some source code, or at
the very least
the part of your code which triggers the assert.

You most likely called a function on your surface which failed and set the
status to "error", but didn't detect this and attempted to call another
function on said surface.
Mind you, my knowledge of cairo is very limited, so that is just an
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