[PATCH 6/6] devtools: forbid direct use of sys/queue.h

[Stephen Hemminger <stephen@networkplumber.org>]

The set of list macros provided by <sys/queue.h> differs per platform:
glibc lacks the _FOREACH_SAFE variants, and musl and Windows have no such
header. DPDK now provides rte_queue.h with the complete set.

Both headers use the same multiple inclusion guard, so a single direct
include of <sys/queue.h> anywhere in a translation unit disables
rte_queue.h for all of it. Reject new occurrences.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 devtools/checkpatches.sh                 | 9 +++++++++
 doc/guides/contributing/coding_style.rst | 5 ++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/devtools/checkpatches.sh b/devtools/checkpatches.sh
index 18bd825372..a8ff4bfe82 100755
--- a/devtools/checkpatches.sh
+++ b/devtools/checkpatches.sh
@@ -105,6 +105,15 @@ check_forbidden_additions() { # <patch>
 		-f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
 		"$1" || res=1
 
+	# include rte_queue.h, the system header has fewer macros
+	awk -v FOLDERS="lib drivers app examples" \
+		-v SKIP_FILES='lib/eal/include/rte_queue.h' \
+		-v EXPRESSIONS='include.*<sys/queue.h>' \
+		-v RET_ON_FAIL=1 \
+		-v MESSAGE='Using <sys/queue.h>, prefer <rte_queue.h>' \
+		-f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
+		"$1" || res=1
+
 	# check %l or %ll format specifier
 	awk -v FOLDERS='lib drivers app examples' \
 		-v EXPRESSIONS='%ll*[xud]' \
diff --git a/doc/guides/contributing/coding_style.rst b/doc/guides/contributing/coding_style.rst
index 11de3bb39a..f2c2cd8503 100644
--- a/doc/guides/contributing/coding_style.rst
+++ b/doc/guides/contributing/coding_style.rst
@@ -317,11 +317,14 @@ Queues
 ~~~~~~
 
 Use queue(3) macros rather than rolling your own lists, whenever possible.
+Include ``<rte_queue.h>`` rather than ``<sys/queue.h>``:
+the set of macros provided by the system header differs per platform,
+and the DPDK one provides the same complete set everywhere.
 Thus, the previous example would be better written:
 
 .. code-block:: c
 
- #include <sys/queue.h>
+ #include <rte_queue.h>
 
  struct foo {
          LIST_ENTRY(foo) link;      /* Use queue macros for foo lists. */
-- 
2.53.0