The context.push_group() method will cause a segmentation fault if 
(a) a transformation has been defined with a floating point number as argument
(b) a rectangular clipping region is defined using context.rectangle(...) and
context.clip()
(c) the context.push_group() method is called.

The following snippet, which is a variation of the example on the pycairo
homepage, illustrates the bug:


-------
#!/usr/bin/env python

import cairo

WIDTH, HEIGHT = 400, 400

# Setup Cairo
surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, WIDTH, HEIGHT)
ctx = cairo.Context(surface)

# Set thickness of brush
ctx.set_line_width(15)

if 1: # set to 0 or just plain 42 as scaling factor and the segault will go away !
    ctx.translate(100, 42.4344454647)
ctx.rectangle(0, 0, WIDTH, HEIGHT)
ctx.clip()
ctx.push_group()

# Draw out the triangle using absolute coordinates
ctx.move_to(200, 100)
ctx.line_to(300, 300)
ctx.rel_line_to(-200, 0)
ctx.close_path()

ctx.pop_group()

# Apply the ink
ctx.stroke()

# Output a PNG file
surface.write_to_png("triangle.png")

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(I marked the bug as major, because I think a segfault is a major bug).