[RFC v2 11/14] log: add a per line log helper

[David Marchand <david.marchand@redhat.com>]

gcc builtin __builtin_strchr can be used as a static assertion to check
whether passed format strings contain a \n.
This can be useful to detect double \n in log messages.

Signed-off-by: David Marchand <david.marchand@redhat.com>
---
Changes since RFC v1:
- added a check in checkpatches.sh,

---
 devtools/checkpatches.sh |  8 ++++++++
 lib/log/rte_log.h        | 21 +++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/devtools/checkpatches.sh b/devtools/checkpatches.sh
index 10b79ca2bc..10d1bf490b 100755
--- a/devtools/checkpatches.sh
+++ b/devtools/checkpatches.sh
@@ -53,6 +53,14 @@ print_usage () {
 check_forbidden_additions() { # <patch>
 	res=0
 
+	# refrain from new calls to RTE_LOG
+	awk -v FOLDERS="lib" \
+		-v EXPRESSIONS="RTE_LOG\\\(" \
+		-v RET_ON_FAIL=1 \
+		-v MESSAGE='Prefer RTE_LOG_LINE' \
+		-f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
+		"$1" || res=1
+
 	# refrain from new additions of rte_panic() and rte_exit()
 	# multiple folders and expressions are separated by spaces
 	awk -v FOLDERS="lib drivers" \
diff --git a/lib/log/rte_log.h b/lib/log/rte_log.h
index 27fb6129a7..da7e672e81 100644
--- a/lib/log/rte_log.h
+++ b/lib/log/rte_log.h
@@ -17,6 +17,7 @@
 extern "C" {
 #endif
 
+#include <assert.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdarg.h>
@@ -358,6 +359,26 @@ int rte_vlog(uint32_t level, uint32_t logtype, const char *format, va_list ap)
 		 RTE_LOGTYPE_ ## t, # t ": " __VA_ARGS__) :	\
 	 0)
 
+#ifdef RTE_TOOLCHAIN_GCC
+#define RTE_LOG_CHECK_NO_NEWLINE(fmt) \
+	static_assert(!__builtin_strchr(fmt, '\n'), \
+		"This log format string contains a \\n")
+#else
+#define RTE_LOG_CHECK_NO_NEWLINE(...)
+#endif
+
+#define RTE_LOG_LINE(l, t, ...) do { \
+	RTE_LOG_CHECK_NO_NEWLINE(RTE_FMT_HEAD(__VA_ARGS__,)); \
+	RTE_LOG(l, t, RTE_FMT(RTE_FMT_HEAD(__VA_ARGS__,) "\n", \
+		RTE_FMT_TAIL(__VA_ARGS__ ,))); \
+} while (0)
+
+#define RTE_LOG_DP_LINE(l, t, ...) do { \
+	RTE_LOG_CHECK_NO_NEWLINE(RTE_FMT_HEAD(__VA_ARGS__,)); \
+	RTE_LOG_DP(l, t, RTE_FMT(RTE_FMT_HEAD(__VA_ARGS__,) "\n", \
+		RTE_FMT_TAIL(__VA_ARGS__ ,))); \
+} while (0)
+
 #define RTE_LOG_REGISTER_IMPL(type, name, level)			    \
 int type;								    \
 RTE_INIT(__##type)							    \
-- 
2.43.0