[cairo] cairo memory leak

[唐博]

I use cairo as this: 
 
cairo_move_to(cr, pPolyline->pPoints[0].x, pPolyline->pPoints[0].y);
for (s = 1; s < pPolyline->count; ++s)
{ 
  cairo_line_to(cr, pPolyline->pPoints[s].x, pPolyline->pPoints[s].y);
}
cairo_stroke(cr);
it will Memory leak. HookLogger said:
>>>>_tr_malloc <C:\systemapi\src\system\memory\malloc.cpp #7> + 8 - Navidog2X.exe! 4de78a6b()
__pixman_image_allocate <C:\workspaces\map9.1.5\src\XPixman_20110814\src\pixman-image.c #59> + 10 - Navidog2X.exe! 4df505bc()
_pixman_image_create_solid_fill <C:\workspaces\map9.1.5\src\XPixman_20110814\src\pixman-solid-fill.c #77> + 5 - Navidog2X.exe! 4df56c94()
__cairo_format_bits_per_pixel <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo-image-surface.c #1076> + 9 - Navidog2X.exe! 4df3a088()
__cairo_format_bits_per_pixel <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo-image-surface.c #1670> + 8 - Navidog2X.exe! 4df3ba28()
__cairo_format_bits_per_pixel <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo-image-surface.c #3515> + 27 - Navidog2X.exe! 4df3f1e0()
__cairo_format_bits_per_pixel <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo-image-surface.c #2327> + 44 - Navidog2X.exe! 4df3cd61()
__cairo_format_bits_per_pixel <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo-image-surface.c #3579> + 32 - Navidog2X.exe! 4df3f396()
__cairo_format_bits_per_pixel <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo-image-surface.c #3680> + 36 - Navidog2X.exe! 4df3f659()
__cairo_surface_stroke <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo-surface.c #2184> + 41 - Navidog2X.exe! 4df471b4()
__cairo_gstate_stroke <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo-gstate.c #1145> + 96 - Navidog2X.exe! 4df75ffc()
_cairo_stroke_preserve <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo.c #2416> + 20 - Navidog2X.exe! 4df4181d()
_cairo_stroke <C:\workspaces\map9.1.5\src\XCairo_20110815\src\cairo.c #2389> + 8
 
I didn't find some wrong in pixman-image.c and cairo-image-surface.c . Who can tell me the reason.