Created attachment 19908 [details]
Log file

Here is the log for the commit df537046c2130be285b213b5d0478159d1c5b16d .
This bug report is about the first error in the log. The rest are assumed to be duplicates or parts of the cascade.

Created attachment 19919 [details]
Simplified sample file

The uUninitialized values are introduced in

int convert_separation_alternate( ... )
{
        // ...
        gs_client_color cc;

        // ...

        // Should be sizeof(float)*GS_CLIENT_COLOR_MAX_COMPONENTS
        memset(&cc.paint.values, 0x00, GS_CLIENT_COLOR_MAX_COMPONENTS);

        // Why? It is already zeroed.
        cc.paint.values[0] = 0;

        // This function leaves the separation color intact.
        // And writes only 1 component to conc[]
        sep_space->type->concretize_color(&cc, sep_space, conc, pgs, (gx_device *)pdev);

        // The next fragment uses 3 components.
        for (i = 0;i < pdev->color_info.num_components;i++)
            cc.paint.values[i] = frac2float(conc[i]);

        // ...
}

No longer happens. Tested with commit 4ea891719046f38f2d7758f7556d7a291fb1b1ad

Not worth git bisect since it is fixed.