Re: [libmicrohttpd] MHD_start_daemon returns NULL

[Evgeny Grin]

Hi Roel,

Looks like your Linux kernel was compiled without eventfd support. Can 
you check your '.config' for 'CONFIG_EVENTFD'?

The easiest way to build working MHD in such case is use 
'--enable-itc=pipe' configure parameter. It will prevent usage of 
eventfd functions even if eventfd support is detected in headers and libc.

Thanks for your nice report, I'll add more checks in configure to check 
for the real eventfd availability.

--
Evgeny


On 22.12.2022 20:38, Roel Janssen wrote:
> 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

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