RE: stderr output from gnome-shell

[John Frankish <john frankish outlook com>]

> From: gnome-shell-list [mailto:gnome-shell-list-bounces gnome org] On
Behalf Of John Frankish
> Sent: Wednesday, 03 June, 2015 09:57
> To: gnome-shell-list gnome org
> Subject: stderr output from gnome-shell
>
> I've been trying to get stderr messages from gnome-shell-3.16.2.
>
> if I change src/main.c line 400 to read:
>
> int
> main (int argc, char **argv)
> {
>   freopen("/tmp/mystderr.txt", "w", stderr);
>   GOptionContext *ctx;
>   ...
>
> I expected to get JS LOG (I added "log('main.js start ');" to
> js/ui/main.js)
> and JS ERROR messages, but all I get is an empty file /tmp/mystderr.txt
>
> As a test, I modified things to read:
>
> freopen("/tmp/mystderr.txt", "w", stdout); printf("This text is redirected
to mystderr.txt\n");
> ..but again, all I get is an empty file.
>
> Is there a trick to this? How do I get stderr output from gnome-shell
The trick has two parts:

1. to realise that the error was in mutter, not gnome-shell :(

And 

2. freopen("/tmp/mystderr.txt", "w", stderr);
printf("This text is redirected to mystderr.txt\n");
fflush(stderr);