printf output from librfxcodec is block-buffered

[rowlap]

I'm interested in seeing output like rfxcodec_encode_create: got sse4.1 in
https://github.com/neutrinolabs/librfxcodec/blob/devel/src/rfxencode.c

however printf is an unusual choice of logging API.

Specifically, when we connect in a way which calls rfxcodec_encode_create_ex, the printf calls to stdout are block-buffered, the default behaviour for output to a non-terminal.

As such, we see this output going to systemd's journal, but only at the end of the session.

Nov 08 13:56:40 desktop xrdp[20339]: rfxcodec_encode_create: got sse2
Nov 08 13:56:40 desktop xrdp[20339]: rfxcodec_encode_create: got sse3
Nov 08 13:56:40 desktop xrdp[20339]: rfxcodec_encode_create: got sse4.1
Nov 08 13:56:40 desktop xrdp[20339]: rfxcodec_encode_create: got sse4.2
Nov 08 13:56:40 desktop xrdp[20339]: rfxcodec_encode_create: got popcnt
Nov 08 13:56:40 desktop xrdp[20339]: rfxcodec_encode_create: got lzcnt
Nov 08 13:56:40 desktop xrdp[20339]: rfxcodec_encode_create: rfx_encode set to rfx_encode_component_rlgr3_amd64_sse41

I tried changing the service ExecStart config to prefix
stdbuf --output=L ...
which then printed the output on connection, not disconnection.

Throughout the codebase under src/ there are 30 calls to LLOGLN (which is #define'd to printf), and 23 calls to printf directly.

It would be helpful if the [Logging] config from xrdp.ini were reflected in librfxcodec, but at a minimum can we avoid buffered output with printf?