Fix compatibility with ELL 0.45 and later

[mjmartineau]

ELL 0.45 and later have header files that use a trailing semicolon with
the DEFINE_CLEANUP_FUNC() macro, which is not compatible with the
"-pedantic" flag in gcc. This causes the mptcpd code to issue the
following error:

"ISO C does not allow extra ‘;’ outside of a function [-Werror=pedantic]"

Wrap the ELL includes in some pragmas to avoid this error.

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Covered Lines:	1148
Relevant Lines:	1864

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💛 - Coveralls

[ossama-othman]

Do you think it would be overkill to create a private mptcpd header for each ELL header that triggers the pedantic diagnostic? For example, we could have something like the following in <mptcpd/private/util.h>:

// SPDX-License-Identifier: BSD-3-Clause
/**
 * @file private/util.h
 *
 * @brief mptcpd convenience wrapper around <ell/util.h>.
 *
 * Copyright (c) 2022, Intel Corporation
 */

#ifndef MPTCPD_PRIVATE_UTIL_H
#define MPTCPD_PRIVATE_UTIL_H

/*
  ELL 0.45 and later have header files that use a trailing semicolon
  with the DEFINE_CLEANUP_FUNC() macro, which is not compatible with
  the "-pedantic" flag in gcc. This causes the mptcpd code to issue the
  following error:

  "ISO C does not allow extra ‘;’ outside of a function
  [-Werror=pedantic]"

  Wrap the ELL includes in some pragmas to avoid this error.
*/
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpedantic"
#include <ell/util.h>
#pragma GCC diagnostic pop

#endif  // MPTCPD_PRIVATE_UTIL_H


/*
  Local Variables:
  c-file-style: "linux"
  End:
*/

Mptcpd source files would then include <mptcpd/private/util.h> instead of <ell/util.h>, and similarly for other ELL headers that trigger the -pedantic diagnostic. That would allow us to avoid peppering the mptcpd code with lots of #pragma directives, but at the cost of having more files to maintain.

[mjmartineau]

The wrapper headers do seem like a heavier solution to me.

I also considered:

#include <mptcpd/private/util.h>

BEGIN_ELL_INCLUDE
#include <ell/this.h>
#include <ell/that.h>
END_ELL_INCLUDE

where private/util.h (or whatever) has the macro definitions containing the pragmas.

but it doesn't save any lines of code, and at least directly using the pragmas shows any future developer what exactly is going on when they add a new source file.

I don't have strong feelings about the exact flavor of the solution, I just don't want to burn much more time on it...