[libmicrohttpd] MHD_start_daemon returns NULL

[Roel Janssen]

Dear list,

I'm trying to create an HTTP server for an ARMv7 device.
But MHD_start_daemon returns NULL, and I don't know how to go from there.

The device uses kernel:
# uname -a
Linux buildroot 4.0.0-ADI-1.3.0 #1 PREEMPT Thu Sep 15 16:03:17 UTC 2022 armv7l 
GNU/Linux

And libc:
# /lib/libc-2.18.so 
GNU C Library (GNU libc) stable release version 2.18, by Roland McGrath et al.
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 4.8.3.
Compiled on a Linux 4.0.0 system on 2018-04-28.
Available extensions:
        crypt add-on version 2.1 by Michael Glad and others
        GNU Libidn by Simon Josefsson
        Native POSIX Threads Library by Ulrich Drepper et al
        BIND-8.2.3-T5B
libc ABIs: UNIQUE
For bug reporting instructions, please see:
<http://www.gnu.org/software/libc/bugs.html>.


I cross-compiled libmicrohttpd-0.9.75 with --enable-messages, and call 
MHD_start_daemon as
following:
daemon = MHD_start_daemon (MHD_USE_INTERNAL_POLLING_THREAD | MHD_USE_ERROR_LOG,
                           PORT, NULL, NULL, &respond, NULL, MHD_OPTION_END);

Unfortunately, MHD_start_daemon returns NULL. Here's the output snippet of 
strace:

write(1, "Starting HTTP server.\n", 22) = 22
brk(NULL)                               = 0x5a000
brk(0x7b000)                            = 0x7b000
eventfd2(0, EFD_CLOEXEC|EFD_NONBLOCK)   = -1 ENOSYS (Function not implemented)
write(2, "Failed to create inter-thread co"..., 78) = 78

What's going on?  And what can I do?

Kind regards,
Roel Janssen