linux-ext4 - [PATCH] tst_libext2fs: Avoid multiple definition of global variables

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Message-Id: <20200130132122.21150-1-lczerner@redhat.com>
Date:   Thu, 30 Jan 2020 14:21:22 +0100
From:   Lukas Czerner <lczerner@...hat.com>
To:     linux-ext4@...r.kernel.org
Cc:     tytso@....edu
Subject: [PATCH] tst_libext2fs: Avoid multiple definition of global variables

gcc version 10 changed the default from -fcommon to -fno-common and as a
result e2fsprogs unit tests fail because tst_libext2fs.c end up with a
build error.

This is because it defines two global variables debug_prog_name and
extra_cmds that are already defined in debugfs/debugfs.c. With -fcommon
linker was able to resolve those into the same object, however with
-fno-common it's no longer able to do it and we end up with
multiple definition errors.

Fix the problem by creating an extern declaration of said variables in
debugfs.h and just setting them in tst_libext2fs.c without additional
declaration.

Signed-off-by: Lukas Czerner <lczerner@...hat.com>
---
 debugfs/debugfs.h          | 2 ++
 lib/ext2fs/tst_libext2fs.c | 5 +++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/debugfs/debugfs.h b/debugfs/debugfs.h
index 477d9bbb..956517bc 100644
--- a/debugfs/debugfs.h
+++ b/debugfs/debugfs.h
@@ -123,6 +123,8 @@ extern void do_set_block_group_descriptor(int argc, char **, int sci_idx, void *
 extern void do_dump_unused(int argc, char **argv, int sci_idx, void *infop);
 
 /* debugfs.c */
+extern ss_request_table *extra_cmds;
+extern const char *debug_prog_name;
 extern void internal_dump_inode(FILE *, const char *, ext2_ino_t,
 				struct ext2_inode *, int);
 
diff --git a/lib/ext2fs/tst_libext2fs.c b/lib/ext2fs/tst_libext2fs.c
index 3e7497cd..43f0d153 100644
--- a/lib/ext2fs/tst_libext2fs.c
+++ b/lib/ext2fs/tst_libext2fs.c
@@ -28,9 +28,7 @@
  * Hook in new commands into debugfs
  * Override debugfs's prompt
  */
-const char *debug_prog_name = "tst_libext2fs";
 extern ss_request_table libext2fs_cmds;
-ss_request_table *extra_cmds = &libext2fs_cmds;
 
 static int print_blocks_proc(ext2_filsys fs EXT2FS_ATTR((unused)),
 			     blk64_t *blocknr, e2_blkcnt_t blockcnt,
@@ -51,6 +49,9 @@ void do_block_iterate(int argc, char **argv, int sci_idx EXT2FS_ATTR((unused)),
 	int		err = 0;
 	int		flags = 0;
 
+	debug_prog_name = "tst_libext2fs";
+	extra_cmds = &libext2fs_cmds;
+
 	if (common_args_process(argc, argv, 2, 3, argv[0], usage, 0))
 		return;
 
-- 
2.21.1