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=== Description (from pull-request) ===
Originally, the compiler complained:
macro.h:7:25: error: expected expression before ')' token
__func__, __VA_ARGS__);
The reason is that GCC wouldn't abandon `,` when `__VA_ARGS__` is empty.
For emaple:
#define eprintf(format, ...) fprintf (stderr, format, __VA_ARGS__)
eprintf("success!\n", );
→ fprintf(stderr, "success!\n", );
According to GCC doc, it's okay when adding `##` before `__VA_ARGS__`:
#define eprintf(format, ...) fprintf (stderr, format, ##__VA_ARGS__)
eprintf ("success!\n")
→ fprintf(stderr, "success!\n");
From 2a94c281e34f53867ed75fb4c3d00e7c814287d5 Mon Sep 17 00:00:00 2001
From: river <ri...@vvl.me>
Date: Mon, 26 Aug 2019 18:01:12 +0800
Subject: [PATCH] macro: fix lxcfs_{error,debug,v} build error when __VA_ARGS__
is empty
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Originally, the compiler complained:
macro.h:7:25: error: expected expression before ')' token
__func__, __VA_ARGS__);
The reason is that GCC wouldn't abandon `,` when `__VA_ARGS__` is empty.
For emaple:
#define eprintf(format, ...) fprintf (stderr, format, __VA_ARGS__)
eprintf("success!\n", );
→ fprintf(stderr, "success!\n", );
According to GCC doc, it's okay when adding `##` before `__VA_ARGS__`:
#define eprintf(format, ...) fprintf (stderr, format, ##__VA_ARGS__)
eprintf ("success!\n")
→ fprintf(stderr, "success!\n");
---
macro.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/macro.h b/macro.h
index 7213b8f..3e9ef82 100644
--- a/macro.h
+++ b/macro.h
@@ -4,19 +4,19 @@
#define lxcfs_debug_stream(stream, format, ...)
\
do { \
fprintf(stream, "%s: %d: %s: " format, __FILE__, __LINE__, \
- __func__, __VA_ARGS__); \
+ __func__, ##__VA_ARGS__);
\
} while (false)
-#define lxcfs_error(format, ...) lxcfs_debug_stream(stderr, format,
__VA_ARGS__)
+#define lxcfs_error(format, ...) lxcfs_debug_stream(stderr, format,
##__VA_ARGS__)
#ifdef DEBUG
-#define lxcfs_debug(format, ...) lxcfs_error(format, __VA_ARGS__)
+#define lxcfs_debug(format, ...) lxcfs_error(format, ##__VA_ARGS__)
#else
#define lxcfs_debug(format, ...)
#endif /* DEBUG */
#ifdef VERBOSE
-#define lxcfs_v(format, ...) lxcfs_error(format, __VA_ARGS__);
+#define lxcfs_v(format, ...) lxcfs_error(format, ##__VA_ARGS__);
#else
#define lxcfs_v(format, ...)
#endif /* VERBOSE */
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