Re: [dpdk-dev] [PATCHv2] include: fix sys/queue.h.

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

Hi William,

2021-08-11 20:46 (UTC+0000), William Tu:
> Currently there are a couple of header files include 'sys/queue.h',
> which is a POSIX functionality.  When compiling DPDK with OVS on
> Windows, we encountered issues such as, found the missing header.
> In file included from ../lib/dpdk.c:27:
> C:\temp\dpdk\include\rte_log.h:24:10: fatal error: 'sys/queue.h' file
> not found
> 
> The patch fixes it by 1) removing the #include <sys/queue.h> from
> a couple of headers, replace it with  #include <rte_os.h>, and
> 2) include sys/queue.h in the rte_os.h. As a result, for Linux/BSD,
> it is using the sys/queue.h from its POSIX library, and for Windows,
> DPDK will use the bundled sys/queue.h.
> 
> 1) fixes the case that DPDK library shouldn't export POSIX functionality
> into the environment (symbols, macros, headers etc), which cause definitions
> clashing with the application.
> 2) fixes the case that DPDK should depend only on the C library and not
> require POSIX functionality from the underlying system.

Sorry, this is not exactly what was suggested here:

	http://inbox.dpdk.org/dev/20210811013325.34c36220@sovereign/

The point was not to install <sys/queue.h>. Its full content is not needed
for DPDK interface, only for implementation. Public headers only need a
handful of macros for list/tailq heads and links. Those macros should be
provided by DPDK, with RTE_ prefix. For Linux and FreeBSD it will just be:

	#include <sys/queue.h>
	#define RTE_TAILQ_ENTRY(type) TAILQ_ENTRY(type)
	/* ... */

For Windows you would have to copy definitions from <sys/queue.h>
to some public header, <rte_os.h> seems OK. All public headers that need
<sys/queue.h> macros must have them replaced with RTE_ version.
Implementation remains unchanged. No new files need to be installed,
because when DPDK is built on Windows, it uses the bundled <sys/queue.h>,
and when it is installed, only RTE_ macros you created are visible.

Macro documentation should clearly state that they are compatible with system
<sys/queue.h> for Linux and FreeBSD, and for Windows they are compatible with
the version used during build.

+Bruce, David, Ray, Tyler to confirm/object the idea.

> There are still a couple of headers using sys/queue.h, ex:
> rte_bus_pci.h. Since it's not been used in Windows yet, we can
> fix them later.

Another item I think of is a checkpatch rule to prohibit TAILQ_xxx, etc
macro in public headers after replacing them all.

> Suggested-by: Nick Connolly <nick.connolly@mayadata.io>
> Suggested-by: Dmitry Kozliuk <Dmitry.Kozliuk@gmail.com>
> Signed-off-by: William Tu <u9012063@gmail.com>
> ---
> v1->v2:
>   - follow the suggestion by Nick and Dmitry 
>   - http://mails.dpdk.org/archives/dev/2021-August/216304.html

Please send new versions as replies to the previous ones:

	git send-email --in-reply-to MSGID ...

https://doc.dpdk.org/guides/contributing/patches.html